Frequently Asked Questions for CS410X-LIST and CS411X-LIST

1. AWT Questions

1.1 Image Questions

¥ How do I convert 3 short arrays, r, g and b into an image?

¥ How do I build an image in memory?

¥ How do I load an Image?

¥ How do I place a component on a background image?

¥ How to display an image (sequence)?

¥ How do I grab a frame?

¥ How do I convert from pict to image?

¥ how do I time image processing?

1.2 Graphics Questions

¥ How do I find the screen size and resolution?

¥ How do I nest layouts in panels?

¥ How do I use Gridbag Layout?

¥ How do I use grid layout?

¥ How do I add a couple of panels to a frame?

¥ How do I intersect a ray with an ellipse?

¥ How do I intersect a ray with an ellipse (Code Example)?

¥ How do I nest layouts in panels?

¥ How do I draw Points in 3D in Java?

1.3 Event Questions

¥ How do I move Components?

¥ How do I move Components (Code Example)?

¥ How do I use movable components in an interface?

¥ How do I set the location of a component?

1.4 Other AWT Questions

¥ How do you account for PEER classes?

¥ How do I put a gui on my stock quotes?

2. File IO Questions

¥ How do I process a line at a time?

¥ How do I build a custom streamtokenizer?

¥ How should I save to a file?

¥ How do I read and write gzipped objects with java?

¥ How do I display a directory?

¥ How to I read and Write a gzipped file of floats?

¥ How do I set the pict file type?

¥ How do I buffer output in Java?

¥ How do I copy a file in Java?

3. NET Questions

¥ How do I send e-mail in Java?

¥ How do I get an a name from an IP address in Java?

¥ How do I check my mail with Java?

¥ How do I get an address from a name in Java?

¥ How do I do a client server with sockets in Java?

¥ How do I build servelets in Java?

4. Keyboard Input Questions

¥ How do I make a system console?

¥ How do I parse a string?

¥ How do I convert a string to an int?

¥ How do I build a command line Interpreter?

¥ How do you determine a key-code?

¥ How do I figure out what modifiers are pressed?

¥ How can I obtain a consistent keyboard mapping?

¥ How can I print all the key-event info?

¥ How do I drive a serial line-based controller?

5. Threads Questions

¥ How do you set alarms in Java?

¥ How do I do implicit threading?

6. Util Questions

¥ How do I get Stockquotes in Java?

7. Multimedia Questions

¥ How do I play notes in Java?

¥ How do I capture a video sequence?

¥ How do I set the flags to grab a frame?

¥ How do I get a printed copy of QT-Components?

¥ how do I get QT4Java?

¥ How do I learn about digitizing video?

7. Miscellaneous Questions

¥ How do I get the methods from a class?

¥ How do I write help?

¥ How do I add meta tags?

¥ How do I use a jar file?

¥ How do I serialize an object?

¥ How do I unsubscribe?

¥ How do I set up for browsing?

¥ How do I make a Jar file from many directories?

¥ How do I tell the type of an object?

¥ How do I hand in Late homework?

¥ How do I get the author tag in JavaDoc?

¥ How do I find javadoc?

¥ How do I know if a class can be public?

¥ How do I make Javadoc work on non-public files?

¥ How do I draw BNF Diagrams?

¥ How do you uncompress a Jar file?

¥ How do I run an application with codewarrior?

¥ How do I add jars to my class path?

¥ How do I compile diffcad?

¥ How do I pack an Array of bytes?

¥ How do I playback quicktime movies in Java?

¥ How do I set the com port?

¥ How do I install Java programs on Solaris/win95/winnt?

¥ How do I update codewarrior?

¥ How do I add features to a class?

¥ How do I find Kahindu?

¥ How do I get tech-support from Metrowerks?

¥ How do I run Java using CGI?

¥ How do I design my programs?

¥ How do I describe a problem to get help?

¥ How do you run a makefile?

¥ How do I install Java3D?

¥ How will I earn a grade in Embedded Control?

¥ How do I install the COMM API on NT?

¥ How do I run quick-time for Java, under windows?

How do I convert 3 short arrays, r, g and b into an image?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I convert 3 short arrays, r, g and b into an image?

Date: Wed, 4 Nov 1998 15:57:18 -0400

public Image short2Image(short r[][],short g[][], short b[][]) {

int width = r.length;

int height = r[0].length;

Toolkit tk = Toolkit.getDefaultToolkit();

int pels[] = new int[width*height];

for (int x = 0; x < width; x++)

for (int y = 0; y < height; y++) {

pels[ x + y * width] =

0xff000000

| (r[x][y] << 16)

| (g[x][y] << 8)

| b[x][y];

}

return tk.createImage(

new MemoryImageSource(

width,

height,

ColorModel.getRGBdefault(),

pels, 0,

width));

}

How do I build an image in memory?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I build an image in memory?

Date: Sun, 22 Nov 1998 09:47:29 -0400

import java.awt.*;

import java.awt.image.*;

public class MemImage extends java.applet.Applet

{

Image i;

int pixel[]; // The memory array, one int is one pel.

int w=300; // Image width and height in pels

int h=200;

int RED=0xffff0000; // Some typical pel values

int GREEN=0xff00ff00;

int BLUE=0xff0000ff;

int BLACK=0xff000000;

public void init()

{

pixel=new int[h*w];

for(int i=0;i<h;i++)

for(int j=0;j<w;j++)

if(i==0 || j==0 || i==h-1 || j==w-1)

pixel[w*i+j]=BLACK; // Draw a border

else if(j<100)pixel[w*i+j]=RED;

else if(j<200)pixel[w*i+j]=GREEN;

else pixel[w*i+j]=BLUE;

i=createImage(new MemoryImageSource(w,h,pixel,0,w));

}

public void paint(Graphics g)

{

g.drawImage(i,50,50,this);

}

}

How do I load an Image

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I load an Image

Date: Sun, 22 Nov 1998 09:47:29 -0400

import java.awt.*;

class LoadImage extends Frame

{

Image i;

// Images are loaded asynchronously - you need a tracker to know

when complete

MediaTracker tracker;

LoadImage()

{

super("LoadImage");

i=Toolkit.getDefaultToolkit().getImage("background.gif");

tracker = new MediaTracker(this);

tracker.addImage(i,0);

// ... do other useful work here ...

try{tracker.waitForID(0);}catch(Exception e){}

setBackground(Color.red);

reshape(0,0,180,180);

show();

}

static public void main(String args[]) { new LoadImage(); }

public boolean handleEvent(Event e)

{

if(e.id==Event.WINDOW_DESTROY)System.exit(0);

return(super.handleEvent(e));

}

public void paint(Graphics g)

{

g.drawImage(i,50,50,this);

}

}

How do I place a component on a background image?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I place a component on a background image?

Date: Sun, 22 Nov 1998 09:47:29 -0400

import java.awt.*;

public class Background extends Frame

{

Image

background=Toolkit.getDefaultToolkit().getImage("background.gif");

// If running as an applet use the following instead

// Image background=getImage(getCodeBase(),"background.gif");

ImagePanel p;

Button b=new Button("Press");

Background()

{

super("Background");

setLayout(new FlowLayout());

reshape(0,0,150,150);

MediaTracker tracker=new MediaTracker(this);

tracker.addImage(background,0);

try{tracker.waitForID(0);}catch(Exception e){}

p=new ImagePanel(background);

p.add(b);

add(p);

Thread.yield();

show();

}

public boolean handleEvent(Event e)

{

if(e.id==Event.WINDOW_DESTROY)

System.exit(0);

show();

return(super.handleEvent(e));

}

public static void main(String args[]){new Background();}

}

class ImagePanel extends Panel

{

Image background;

Dimension d=new Dimension();

ImagePanel(Image b)

{

background=b;

d.width=background.getWidth(null);

d.height=background.getHeight(null);

d.width=80;

d.height=80;

}

public Dimension preferredSize()

{

return(d);

}

public void paint (Graphics g)

{

g.drawImage(background,0,0,null);

g.drawRect(0,0,d.width-1,d.height-1);

}

}

how do I find the screen size and resolution?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: how do I find the screen size and resolution?

Date: Sun, 22 Nov 1998 09:47:29 -0400

import java.awt.*;

public class Screen extends java.applet.Applet

{

public void init()

{

Toolkit t=Toolkit.getDefaultToolkit();

add(new Label("Dots per inch is "+t.getScreenResolution()));

add(new Label("Screen size is "+t.getScreenSize()));

}

}

How do I process a line at a time?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I process a line at a time?

Date: Wed, 11 Nov 1998 16:50:20 -0400

To process one line of text at a time, look at:

public static void processJava() {

FileInputStream fis = getFileInputStream();

String line;

DataInputStream dis = new DataInputStream(fis);

System.out.println("<HTML><BODY><PRE>");

try { while ((line = dis.readLine()) != null)

System.out.println(line);

}

catch (IOException e) {

System.out.println("Futil: ER! in processJava");

}

System.out.println("</PRE></BODY></HTML>");

closeInputStream(fis);

}

See how readLine returns a string? This enables you to

scan a document for entire words. How would you

read a statement in Java at a time?

Would you use a streamtokenizer? How would you set

the syntax?

Look Futil.java over very carefully!!

Please feel free to ask questions.

Regards,

- DL

-------- Futil.java follows:

package futils;

import java.util.*;

import java.awt.*;

import java.io.*;

public final class Futil {

/**

* Don't let anyone instantiate this class.

*/

private Futil() {}

public static String getReadFileName() {

Frame frm = new Frame();

frm.setSize(100,100);

FileDialog dialog = new FileDialog(frm, "select file");

dialog.show();

String file_name = dialog.getFile();

String path_name = dialog.getDirectory();

String file_string = path_name + file_name;

System.out.println("Opening file: "+file_string);

dialog.dispose();

return file_string;

}

public static FileOutputStream getWriteFileOutputStream() {

try {

return

new FileOutputStream(getWriteFileName());

}

catch (Exception e) {

System.out.println("Er: FileOutputStream in futils.java");}

return null;

}

public static String getWriteFileName() {

FileDialog dialog = new FileDialog(new Frame(), "Enter file

name",FileDialog.SAVE);

dialog.show();

String fs = dialog.getDirectory() + dialog.getFile();

System.out.println("Opening file: "+fs);

dialog.dispose();

return FilterFileNameBug(fs);

}

public static String getWriteDirectoryName() {

FileDialog dialog = new FileDialog(new Frame(), "Enter file

name",FileDialog.SAVE);

dialog.show();

String fs = dialog.getDirectory();

System.out.println("Opening file: "+fs);

dialog.dispose();

return FilterFileNameBug(fs);

}

// Some versions of windows will

// create a .* suffix on a file name

// The following code will strip it:

public static String FilterFileNameBug(String fname) {

if (fname.endsWith(".*.*")) {

fname=fname.substring(0, fname.length() - 4);

}

return fname;

}

public static File getWriteFile() {

return new File(getWriteFileName());

}

public static File getDirFile() {

return new File(Ls.getDirName());

}

public static File getReadFile() {

return new File(getReadFileName());

}

public static FileInputStream getFileInputStream() {

return getFileInputStream(getReadFileName());

}

public static FileInputStream getFileInputStream(String name) {

FileInputStream fis = null;

try

{fis = new FileInputStream(name);}

catch (IOException e)

{System.out.println("futil:Could not open file");}

return fis;

}

public static FileInputStream getFileInputStream(File file) {

FileInputStream fis = null;

try

{fis = new FileInputStream(file);}

catch (IOException e)

{System.out.println("futil:Could not open file");}

return fis;

}

public static FileOutputStream getFileOutputStream() {

FileOutputStream fos = null;

try {fos =

new FileOutputStream(getWriteFileName());

}

catch (IOException e) {

System.out.println("futil:Could not create file");

}

return fos;

}

// Open the file, return -1 if file cannot be opened

// otherwise return the size in bytes

public static int available(File file) {

FileInputStream fis = null;

int sizeInBytes = -1;

try {

fis = new FileInputStream(file);

sizeInBytes = fis.available();

fis.close();

}

catch (IOException e)

{System.out.println("Futil:Could not open file");}

return sizeInBytes;

}

public static void closeOutputStream(OutputStream os) {

try {os.close();} // end try

catch (IOException exe)

{System.out.println("futil: could not close output stream");}

}

public static void closeInputStream(InputStream is) {

try {is.close();} // end try

catch (IOException exe)

{System.out.println("futil: could not close input stream");}

}

public static void lsWordPrintMerge() {

String wild = "pict";

String[] files = Ls.getWildNames(wild);

System.out.println(files.length + " file(s):");

for (int i=0; i < files.length; i++)

System.out.println("\t" + files[i]);

}

static public void filterHtmls() {

String[] files = Ls.getWildNames(".html");

File input_dir = getDirFile();

System.out.println(files.length + " file(s) to process");

File output_dir = new File(input_dir.getParent(),"out");

if (output_dir.exists())

{System.out.println("Output dir exists:"+

output_dir);}

else {output_dir.mkdir();}

for (int i=0; i < files.length; i++) {

writeFilteredHrefFile(input_dir+files[i],output_dir+"/"+files[i]);

}

}

public static void writeFilteredHrefFile(String inputName, String

outputName) {

System.out.println("Filtering:\t" + inputName +"\t>\t"+outputName);

try {

FileInputStream is = new FileInputStream(inputName);

StreamTokenizer tokens = new StreamTokenizer(is);

FileOutputStream os = new FileOutputStream(outputName);

PrintStream output = new PrintStream(os);

int i;

int next = 0;

tokens.resetSyntax();

tokens.wordChars(0,255);

tokens.quoteChar('"');

while ((next = tokens.nextToken()) != tokens.TT_EOF) {

switch (next) {

case '"':

output.print('"');

for (i=0;i<tokens.sval.length();i++)

if (tokens.sval.charAt(i) == ' ')

output.print("%20");

else

output.print(tokens.sval.charAt(i));

output.print('"');

break;

case tokens.TT_WORD:

output.print(tokens.sval+" ");

break;

case tokens.TT_NUMBER:

output.print(tokens.nval+" ");

break;

case tokens.TT_EOL:

output.println();

break;

} // end switch

} // end while

is.close();

os.close();

} // end try

catch (Exception exe)

{System.out.println("writeFilteredHrefFile:er!");}

}

public static void main(String[] args) {

String name = getReadFileName( ) ;

System.out.println("HEllo world, I got:"+name);

try {

System.in.read(); // prevent console window from

going away

} catch (java.io.IOException e) {}

}

public static void writeFilteredJavaFile( ) {

try {

FileInputStream is = getFileInputStream();

StreamTokenizer tokens = new StreamTokenizer(is);

PrintStream output = System.out;

int i;

int next = 0;

tokens.resetSyntax();

tokens.wordChars(0,255);

tokens.quoteChar(';');

while ((next = tokens.nextToken()) != tokens.TT_EOF) {

switch (next) {

case ';':

output.print("got a line:"+tokens.lineno());

break;

case tokens.TT_WORD:

output.print(tokens.sval+" ");

break;

case tokens.TT_NUMBER:

output.print(tokens.nval+" ");

break;

case tokens.TT_EOL:

output.println();

break;

} // end switch

} // end while

is.close();

} // end try

catch (Exception exe)

{System.out.println("writeFilteredHrefFile:er!");}

}

public static void list_filtered_href_file(String file) {

System.out.println("processing:\t" + file);

try {

FileInputStream input_file = new

FileInputStream(file);

StreamTokenizer tokens = new

StreamTokenizer(input_file);

int next = 0;

tokens.resetSyntax();

tokens.wordChars(0,255);

tokens.quoteChar('"');

while ((next = tokens.nextToken()) != tokens.TT_EOF)

{

switch (next) {

case '"':

System.out.print('"');

StringTokenizer st =

new

StringTokenizer(tokens.sval," ");

while (st.hasMoreTokens()) {

System.out.print(st.nextToken());

if

(st.countTokens() > 1)

{System.out.print("%20");}

}

System.out.print('"');

break;

case tokens.TT_WORD:

System.out.print(tokens.sval+" ");

break;

case tokens.TT_NUMBER:

System.out.print(tokens.nval+" ");

break;

case tokens.TT_EOL:

System.out.println();

break;

}

}

System.out.println();

input_file.close();

}

catch (Exception exe)

{System.out.println("list_filtered_href_file:er!");}

}

public static void filterFileHrefs() {

FileInputStream fis = getFileInputStream();

StreamTokenizer tokens = new StreamTokenizer(fis);

int next = 0;

tokens.resetSyntax();

tokens.wordChars(0,255);

tokens.quoteChar('"');

try { while ((next = tokens.nextToken())

!= tokens.TT_EOF) {

switch (next) {

case '"':

System.out.print('"');

StringTokenizer st =

new StringTokenizer(tokens.sval," ");

while (st.hasMoreTokens()) {

System.out.print(st.nextToken());

if (st.countTokens() > 1)

{System.out.print("%20");}

}

System.out.print('"');

break;

case tokens.TT_WORD:

System.out.print(tokens.sval+" ");

break;

case tokens.TT_NUMBER:

System.out.print(tokens.nval+" ");

break;

case tokens.TT_EOL:

System.out.println();

break;

} // switch

}} // try while

catch (IOException e) {

System.out.println("Futil:ER! filterFileHrefs");

}

System.out.println();

closeInputStream(fis);

}

public static void processJava() {

FileInputStream fis = getFileInputStream();

String line;

DataInputStream dis = new DataInputStream(fis);

System.out.println("<HTML><BODY><PRE>");

try { while ((line = dis.readLine()) != null)

System.out.println(line);

}

catch (IOException e) {

System.out.println("Futil: ER! in processJava");

}

System.out.println("</PRE></BODY></HTML>");

closeInputStream(fis);

}

public void lowerFileNames( File thePath ){

String[] fileNames = thePath.list();

String pathstr = thePath.getPath();

for( int i=0;

fileNames != null &&

i< fileNames.length; i++ ) {

String aFileName = fileNames[ i ];

String newFileName = aFileName.toLowerCase();

File theFile = new File( pathstr, aFileName );

if( theFile.isFile() ){

//rename theFile to lower case

System.out.print( i+":" + aFileName );

theFile.renameTo( new File( pathstr, newFileName ) );

System.out.println( "\t==>\t"+newFileName );

}else{

//case theFile is Dir, in the Dir, repeat same procedure

System.out.println( "Dir:"+aFileName );

lowerFileNames( new File( pathstr+aFileName ));

}

}

return;

}//lowerFileNames

public static void makeTocHtml() {

File dir = getDirFile();

String[] files = dir.list(new FileFilter());

System.out.println(files.length + " file(s):");

FileOutputStream fos = getFileOutputStream();

PrintStream ps = new PrintStream(fos);

ps.println("<HTML>");

ps.println("<BODY>");

ps.println("<ul>");

for (int i=0; i < files.length; i++)

ps.println("<LI><a href = \"" + files[i]+"\">"+

files[i]+"</a><P>");

ps.println("</ul>");

ps.println("</BODY>");

ps.println("</HTML>");

closeOutputStream(fos);

}

public static void readDataFile(String file,double data[]) {

System.out.println("processing:\t" + file);

FileInputStream inputFile =

getFileInputStream(file);

StreamTokenizer tokens = new StreamTokenizer(inputFile);

int next = 0;

int num = 0;

try {

while ((next = tokens.nextToken()) != tokens.TT_EOF) {

switch (next) {

case tokens.TT_WORD:

break;

case tokens.TT_NUMBER:

data[num] = (double) tokens.nval;

System.out.println(num+": "+ data[num]);

num = num + 1;

break;

case tokens.TT_EOL:

break;

}

}

}

catch (Exception exe)

{System.out.println("listFilteredHrefFile:er!");}

closeInputStream(inputFile);

}

}

How do I build a custom streamtokenizer?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I build a custom streamtokenizer?

Date: Wed, 11 Nov 1998 16:50:20 -0400

In the last class, I covered

the building of a custom stream tokenizer.

Sorry to say, I forgot the reset for the

syntax. What follows is an excerpt from

the futils program that shows you how

to reset the syntax on the stream tokenizer:

public static void filterFileHrefs() {

FileInputStream fis = getFileInputStream();

StreamTokenizer tokens = new StreamTokenizer(fis);

int next = 0;

tokens.resetSyntax();

tokens.wordChars(0,255);

tokens.quoteChar('"');

try { while ((next = tokens.nextToken())

!= tokens.TT_EOF) {

switch (next) {

case '"':

System.out.print('"');

//Hey class, check out the use of the

// StringTokenizer...pretty neat, huh?

StringTokenizer st =

new StringTokenizer(tokens.sval," ");

//I took the string from the stream tokenizer, then

// processed it more with the string tokenizer....

// The " " used in the constructor gives us the delimiter

// for the string tokenizer....the tokens.sval gives

// us the string to parse for this string tokenizer....

// So, the stream tokenizer is set to stop at quote marks...

// but the string tokenizer stops at spaces...according to

// this usage. Got it? See the end of chapter 4 for

// more info (pp 208-210 for people with a book)....DL

while (st.hasMoreTokens()) {

System.out.print(st.nextToken());

if (st.countTokens() > 1)

{System.out.print("%20");}

}

System.out.print('"');

break;

case tokens.TT_WORD:

System.out.print(tokens.sval+" ");

break;

case tokens.TT_NUMBER:

System.out.print(tokens.nval+" ");

break;

case tokens.TT_EOL:

System.out.println();

break;

} // switch

}} // try while

catch (IOException e) {

System.out.println("Futil:ER! filterFileHrefs");

}

System.out.println();

closeInputStream(fis);

}

How should I save to a file?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How should I save to a file?

Date: Sat, 21 Nov 1998 08:39:45 -0400

r,g, and b are three arrays of short being written

into a gzip file....

- DL

public void saveAsShortgz(String fn) {

Timer t = new Timer();

t.start();

try {

FileOutputStream fos = new FileOutputStream(fn);

GZIPOutputStream gos = new GZIPOutputStream(fos);

ObjectOutputStream oos = new ObjectOutputStream(gos);

oos.writeObject(r);

oos.writeObject(g);

oos.writeObject(b);

oos.close();

gos.finish();

} catch(Exception e) {

System.out.println("Save saveAsShortgz:"+e);

}

t.stop();

t.print(" saveAsShortgz in ");

}

private void readShortsGz(String fn){

Timer t = new Timer();

t.start();

GZIPInputStream in = null;

try {

in = new GZIPInputStream(

new FileInputStream(fn));

} catch(Exception e)

{e.printStackTrace();}

getShortImageGz(in);

t.print("End ReadShorts");

}

How do I read and write gzipped objects with java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I read and write gzipped objects with java?

Date: Sat, 21 Nov 1998 09:54:55 -0400

Here is an example of how to treat objects

as compressed file streams for reading and writing....

public static void main(String args[]) {

System.out.println("Test");

SaveFrame f = new SaveFrame("save frame");

f.show();

float flt[][] =

{

{1.0f,3.0f,4.0f},

{1.0f,3.0f,4.0f},

{1.0f,3.0f,4.0f}

};

String fn = f.getSaveFileName("flt.gz file");

f.saveAsFloatgz(fn,flt);

f.readAsFloatgz(fn,flt);

for (int i=0; i < flt.length; i++)

for (int j=0; j < flt[0].length; j++){

System.out.println(flt[i][j]);

}

}

public void saveAsFloatgz(float f[][]) {

saveAsFloatgz(

getSaveFileName("flt.gz file"), f);

}

public static void saveAsFloatgz(String fn, float f[][]) {

try {

FileOutputStream fos = new FileOutputStream(fn);

GZIPOutputStream gos = new GZIPOutputStream(fos);

ObjectOutputStream oos = new ObjectOutputStream(gos);

oos.writeObject(f);

oos.close();

gos.finish();

} catch(Exception e) {

System.out.println("Save saveAsFloatgz:"+e);

}

}

public static void readAsFloatgz(String fn, float f[][]) {

try {

FileInputStream fis = new FileInputStream(fn);

GZIPInputStream gis = new GZIPInputStream(fis);

ObjectInputStream ois = new ObjectInputStream(gis);

f = (float [][])ois.readObject();

ois.close();

} catch(Exception e) {

System.out.println("Save readAsFloatgz:"+e);

}

}

public String getSaveFileName(String prompt) {

FileDialog fd = new

FileDialog(this, prompt, FileDialog.SAVE);

fd.setVisible(true);

fd.setVisible(false);

String fn=fd.getDirectory()+fd.getFile();

if (fd.getFile() == null) return null; //usr canceled

return fn;

}

how do I display a directory?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: how do I display a directory?

Date: Sun, 22 Nov 1998 09:47:29 -0400

// Vaguely useful program: Displays subtree of any directory showing how many

// files and their total length. (Useful when trying to reclaim disk space)

import java.io.*;

class Tree

{

static String indent=""; // Build tree-like indentation

long total=0; // Tot up storage used

int files=0; // Count files in directory

int dirs=0; // Count sub-directories

Tree(String path,boolean first) // Are we first subtree?

{

indent+=first ? " " : "3 ";

int i;

for(i=path.length();i>0 && path.charAt(i-1)=='\\';i--); // Lose

trailing \'s

File f=new File(path.substring(0,i));

String name[]=f.list(); // Get all the files in this directory

if(name!=null)

for(i=0;i<name.length;i++)

{

String temp=path+File.separator+name[i]; // Rebuild full path

f=new File(temp);

if(f.isDirectory()) // Does this name represent a

sub-directory/

{Tree t=new

Tree(temp,dirs==0);dirs++;total+=t.total;files+=t.files;}

else {files++;total+=f.length();} // If a file, then just add

in its length

}

indent=indent.substring(0,indent.length()-2); // Unwind indentation

System.out.println(indent+(first ? "ÚÄ" : "ÃÄ")+back(path)+"

"+files+","+total);

}

String back(String path) // Return last name in a path

{

int i=path.lastIndexOf(File.separator);

return(path.substring(i+1));

}

public static void main(String args[])

{

if(args.length==0)

{

String dir = System.getProperty( "user.dir" );

new Tree(dir,true); // Display current directory & subtree

}

else if(args.length==1)

new Tree(args[0],true);// Display specific directory

else

System.out.println("Requires directory name");

}

}

How do I send e-mail in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I send e-mail in Java?

Date: Thu, 12 Nov 1998 09:27:58 -0400

package net;

import java.applet.*;

import java.awt.*;

import java.net.*;

import java.io.*;

import java.util.Date;

import gui.ClosableFrame;

public class SendMail extends Applet

{

// The e-mail address all messages are to be sent to; specified in HTML

String webmasterEmail = null;

String serverHostName = null;

boolean standalone = false;

int smtpPort = 25;

Socket socket;

PrintStream ps;

DataInputStream dis;

InetAddress rina;

InetAddress lina;

Form form;

/**

* Initialize the applet.

*/

public void init()

{

setBackground(Color.white);

form = new Form(this);

add(form);

resize(600, 450);

if (serverHostName == null) serverHostName =

getCodeBase().getHost();

if (webmasterEmail == null) webmasterEmail =

getParameter("RECIPIENT");

}

/**

* Show status to the user.

*/

public void showStatus(String s)

{

System.out.println(s);

if (standalone) return;

super.showStatus(s);

}

/**

* Send an e-mail message.

*/

public void send()

throws IOException, Exception

{

// Open connection to SMTP server

socket = new Socket(serverHostName, smtpPort);

// Send the form contents as a message

try

{

rina = socket.getInetAddress();

lina = rina.getLocalHost();

ps = new PrintStream(socket.getOutputStream());

dis = new DataInputStream(socket.getInputStream());

// Send message

sendline("HELO " + lina.toString());

sendline("MAIL FROM:" + form.email());

sendline("RCPT TO:" + webmasterEmail);

sendline("DATA");

sendline(form.message());

sendline(".");

}

catch (Exception ex)

{

socket.close();

throw ex;

}

// Close connection

socket.close();

}

/**

* Send a line of data to the server, and retrieve the handshake

*/

void sendline(String data)

throws IOException

{

System.out.println("sendline out:" + data);

ps.println(data);

ps.flush();

String s = dis.readLine();

System.out.println("sendline in:" + s);

}

/**

* Main routine, for standalone program execution

*/

public static void main(String args[])

{

SendMail ap = new SendMail();

// The server host will be the place running POP

// webmaster e-mail will be recipient

ap.serverHostName = "yourmailserver";

ap.webmasterEmail = "your email address";

ap.standalone = true;

ClosableFrame fr = new ClosableFrame("SendMail");

ap.init();

fr.add("Center", ap);

fr.resize(600, 450);

fr.show();

ap.start();

}

}

/**

* A form for obtaining user input. Customize this for your application, just

* as you would customize an HTML form for a Web-based e-mail application.

*/

class Form extends Panel

{

SendMail applet;

// The form's elements...

Label nameLabel;

TextField nameField;

Label emailLabel;

TextField emailField;

Label orgLabel;

TextField orgField;

Label msgBodyLabel;

TextArea msgBodyArea;

Button sendButton;

/**

* The constructor

*/

public Form(SendMail ap)

{

applet = ap;

setBackground(Color.white);

setLayout(new GridLayout(2, 1));

// Create a panel to put the text fields and button on

Panel p = new Panel();

p.setLayout(new GridLayout(8, 1));

// Instantiate all the elements, and add them to their

containers...

p.add(sendButton = new Button("Send"));

p.add(nameLabel = new Label("Your Name:"));

p.add(nameField = new TextField(60));

p.add(emailLabel = new Label("Your e-mail address:"));

p.add(emailField = new TextField(60));

p.add(orgLabel = new Label("Your orgainization:"));

p.add(orgField = new TextField(60));

p.add(msgBodyLabel = new Label("Your Message:"));

add(p);

add(msgBodyArea = new TextArea(3, 60));

// Set the size of the form

resize(550, 400);

}

/**

* Return the value in the e-mail address field in the form

*/

public String email()

{

return emailField.getText();

}

/**

* Return the contents of the body of the form, including any

"hidden" fields.

*/

public String message()

{

String m = "";

m += nameLabel.getText();

m += nameField.getText();

m += "\n";

m += orgLabel.getText();

m += orgField.getText();

m += "\n";

m += "Web Origin:";

if (!applet.standalone) m += applet.getDocumentBase();

m += "\n";

m += "Date Sent:";

m += (new Date()).toString();

m += "\n";

m += msgBodyLabel.getText();

m += msgBodyArea.getText();

m += "\n";

return m;

}

/**

* Respond to the button click event: send the message.

*/

public boolean handleEvent(Event e)

{

if ((e.target == sendButton) && (e.id == Event.ACTION_EVENT))

{

// User clicked the Send button; send the message

try {applet.send();}

catch (Exception ex)

{

applet.showStatus("Error; message send

failed:\n " + ex.toString());

return true;

}

applet.showStatus("Message sent");

return true;

}

// Not an event to handle; let the super class try

return super.handleEvent(e);

}

}

How do I get an a name from an IP address in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I get an a name from an IP address in Java?

Date: Thu, 12 Nov 1998 09:27:58 -0400

package net;

import java.net.InetAddress;

public class DNS {

public static void getName(String name)

throws Exception

{

try {

InetAddress address =

InetAddress.getByName(name);

byte IP[] = address.getAddress();

for (int index = 0; index < IP.length;

index++) {

if (index > 0)

System.out.print(".");

System.out.print(

((int)IP[index])&

0xff);

}

System.out.println();

}

catch (Exception e)

{System.out.println(

"Feh, that was not a valid name!");}

} // getName

}

How do I make a system console?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I make a system console?

Date: Wed, 2 Dec 1998 05:52:31 -0400

//===========================================================================

// SystemInput.java © 1996-1998 Metrowerks Inc. All

rights reserved.

//===========================================================================

//

// Created: 1/17/97

// Author: Clinton Popetz

// Revised for 1.1 by Scott Kovatch

//

// These two classes just implement a simple System.in stream using a

// TextField

//

// - Cliff McCollum (cliffmcc@gulf.csc.uvic.ca) 8/25/97

//

// Added the option to have all output automatically echoed to the output

// window (like a real System.in would work).

//

// - Cliff McCollum (cliffmcc@gulf.csc.uvic.ca) 11/26/97

// Added support for Java 1.1.4 and CW Pro 2. This involved working around

// a bug in the way BufferedReader and InputStream interact with

// the Metrowerks Java console.

//

// - Make SystemInput the only public class in this file. 3-12-98 -gdb

// - Organize Cliff's ctors differently (main ctor has echo param, empty

// ctor calls main ctor w/ echo true) 3-12-98 -gdb

// - main defaults to echo on, since I like that 3-12-98 -gdb

// - Move newLineChar into SystemInput, since its only used there. 3-12-98 -gdb

// - add cmd line switch to set echo. If there is no switch, it defaults to

on 3-12-98 -gdb

package com.mw;

import java.awt.*;

import java.io.*;

import java.lang.*;

import java.awt.event.*;

interface SystemInConstants {

static final char marker = '\uFFFF';

}

public class SystemInput extends Frame implements SystemInConstants,

KeyListener {

static final char newLineChar = 0x000A;

static SystemInput sFrame; //no GC

SettableStringInputStream stream;

TextField field;

static boolean echoOutput;

// Here's the usage for the arg:

// -echo -> echo is on

// -noecho -> echo is off

// if there is no arg, it defaults to echo on.

public static void main(String [] argv)

{

if (sFrame == null)

{

if (argv.length > 0)

{

if (argv[0].equals("-noecho"))

new SystemInput(false);

else

new SystemInput();

}

else

new SystemInput(); // Let's default to

echo, I like that. -gdb

}

else

sFrame.toFront();

}

public Insets getInsets() {

return new Insets (5, 5, 20, 5);

}

// - Cliff McCollum 8/25/97

// New constructor for receiving echo setting

public

SystemInput(boolean inEcho)

{

super("System.in");

sFrame = this; //no GC

// - Cliff McCollum 8/25/97

// Holds a flag indicating whether we should echo the output.

// On by default.

echoOutput = inEcho;

stream = new SettableStringInputStream(this);

System.setIn(stream);

// - Cliff McCollum 8/25/97

// If we really want this to work like the JDK, then we

should make sure

// we can display at least 80 characters in the input window.

field = new TextField(80);

field.addKeyListener(this);

add("North", new Label("System input should be entered

here."));

add("Center",field);

pack();

show();

}

public

SystemInput()

{

this(true);

}

public void keyPressed(KeyEvent e) {

// If we get a CMD-D, set a marker character in the buffer.

if ((e.getKeyCode() == KeyEvent.VK_E && e.isMetaDown()) ||

e.getKeyCode() == KeyEvent.VK_ENTER) {

String theText = field.getText();

// add the newline to the buffer if an enter or

return was pressed

if (e.getKeyCode() != KeyEvent.VK_E) {

theText += newLineChar;

// - Cliff McCollum 11/27/97

// There is an important behaviour here. If

you use the BufferedReader

// class, it will eventually call

InputStream with a large (8192 bytes)

// buffer. InputStream will keep reading

until this buffer is

// completely full, or it receives an EOF.

To prevent this problem,

// we need to tack an EOF character onto

the end of our buffer

// after every enter or return.

theText += marker;

} else {

// add the marker character to the buffer

theText += marker;

}

stream.MoreData(theText);

field.setText("");

}

}

public void keyTyped(KeyEvent e) {}

public void keyReleased(KeyEvent e) {}

public void toFront()

{

super.toFront();

field.requestFocus();

}

}

class SettableStringInputStream extends InputStream implements

SystemInConstants {

protected String buffer = "";

protected int pos = 0;

protected SystemInput mFrame;

public SettableStringInputStream (SystemInput inNewFrame)

{

mFrame = inNewFrame;

}

public synchronized void MoreData(String data)

{

// - Cliff McCollum 8/25/97

// Here's the echo checking

//

// - Cliff McCollum 11/27/97

// Unfortunately, due to the complications with the

BufferedReader (see above)

// we need to check for the marker character on the end of

this string. If

// it's present, we need to make sure we don't print it.

if (SystemInput.echoOutput) {

String temp = new String(data);

int theLen = temp.length();

if (temp.charAt(theLen-1) == marker) {

temp = temp.substring(0, theLen-2);

}

System.out.print(temp);

// - Cliff McCollum 11/27/97

// We need to print a newline to mimic the

behaviour of Sun's JDK

System.out.print("\n");

}

buffer += data;

notify();

}

public synchronized int read() throws IOException

{

try {

if (buffer.length() <= pos)

{

mFrame.toFront();

wait();

}

char c = buffer.charAt(pos++);

if (c == marker || pos == buffer.length()) //used up this

string, reset it

{

pos = 0;

buffer = "";

}

// If we find the marker char in the buffer, return

-1 for EOF.

if (c == marker)

return -1;

else

return c;

}

catch (InterruptedException e) {

return -1;

}

}

public int available() {

return buffer.length() - pos;

}

}

How do I parse a string: "className.method"

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I parse a string: "className.method"

Date: Mon, 7 Dec 1998 19:35:24 -0400

One way to do this is to use the string methods...another

way is to make an instance of a stream tokenizer.

String s = "className.method";

int i = s.indexOf('.');

OK?

- DL

>Dear Prof.

>

>When the user types:

>className.method

>

>how can I separate className and method name?

>

>Thanks

>Jiyoung An

how do I convert a string to an int?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: how do I convert a string to an int?

Date: Sun, 22 Nov 1998 09:47:29 -0400

class Conv

{

static public void main(String args[])

{

// String to integer

System.out.println(Integer.valueOf("123").intValue());

// Or less confusingly:

String s="123";

Integer i=Integer.valueOf(s);

int j=i.intValue();

System.out.println(j);

// Or better: (parseInt returns int, while valueOf returns Integer)

j=Integer.parseInt("123");

System.out.println(j);

// Convert int to String

i=new Integer(j);

s=i.toString();

System.out.println(s);

// which is the same as

System.out.println(new Integer(j).toString());

}

}

How do I get the methods from a class?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I get the methods from a class?

Date: Thu, 3 Dec 1998 09:44:37 -0400

To get the methods from a class, use:

Class c = (Class)v.elementAt(i);

System.out.println(c);

printMethods(c.getMethods());

- DL

>Dear Prof,

>I have used getMethod to return an array of methods on the class. I

>wanted to know whether the methods related are of the specific class

>that i pass as parameter for getMethods or all the classes that are

>imported in the program.

>Apurva More

>

>______________________________________________________

>Get Your Private, Free Email at http://www.hotmail.com

How do I write help?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I write help?

Date: Thu, 3 Dec 1998 11:40:30 -0400

Hi All,

If a user types:

help TopFrame

The getMethods() will return all the methods available to

an instance of the TopFrame class. It is OK to print

all the methods, you do not have to differentiate from

super-classes and sub-classes.

I hope that this helps to simplify the homework a little.

Thanks!

- DL

>hi, professor,

>Because getMethods() Returns an array containing Method objects

>reflecting all the public member methods of the class or interface

>represented by this Class object, including those declared by the class

>or interface and and those inherited from

>superclasses and superinterfaces. So if user types 'help className', how

>can we just return all the methods just in the class?

>

>best regards

>zhenheng wang

How to I add meta tags?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How to I add meta tags?

Date: Mon, 9 Nov 1998 10:12:44 -0400

When formulating a web page, it is

very important to have meta tags in the HTML.

This will help search engines index your

web page and thus help people find your

web page.

What follows are a list of some meta tag examples

and further hints:

------- Begin cut ------

<title>Distance Learning Homepage</title>

------- End cut -----

Keyword META Tag:

------- Begin cut ------

<meta name="keywords" content="Digital Signal Processing Java Image

Processing Computer Networks Digitial Design ">

------- End cut -----

Description META Tag:

------- Begin cut ------

<meta name="description" content="Java, Networks, and Java DSP Home

Page">

------- End cut -----

All these tags belong between your <head></head> tags within your HTML

document.

NOTE: If you use an HTML editor (i.e. MS FrontPage, AOLPress, etc.) you may

need to consult the help files to determine how to edit the raw HTML code.

If you liked the tools at SiteOwner.com you may be interested in the other

services we offer:

------------------------------------

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- http://www.submit-it.com

------------------------------------

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- http://www.clicktrade.com

------------------------------------

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- http://www.listbot.com

------------------------------------

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- http://www.positionagent.com

------------------------------------

SiteOwner.com: The ultimate bookmark for web site owners!

- http://www.siteowner.com

how do I use a jar file?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: how do I use a jar file?

Date: Sun, 22 Nov 1998 09:47:29 -0400

// To use this from a jar file:

// javac Jar to produce the normal Jar.class file.

// jar cvf Jar.jar Jar.class to create a jar file with just this class

// jar cvf0 Jar.jar Jar.class does the same thing but with no compression

// <applet code=Jar.class archive=Jar.jar width=400 height=350></applet>

// will cause it to be executed out of Jar.jar

import java.awt.*;

public class jar extends java.applet.Applet

{

Button b=new Button("Jar applet");

public void init()

{

add(b);

}

}

how do I serialize an object?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: how do I serialize an object?

Date: Sun, 22 Nov 1998 09:47:29 -0400

Topics:

Overview

Writing Objects to a Stream

Reading Objects from a Stream

Protecting Sensitive Information

Fingerprints of Classes

Secure Hash Stream

Overview

The capability to store and retrieve Java objects is essential

to building all but the most transient applications. The key

to storing and retrieving objects is representing the state of

objects in a serialized form sufficient to reconstruct the

object(s). For Java objects, the serialized form must be able

to identify and verify the Java classes from which the fields

were saved and to restore those fields to instances of the

same classes. The serialized form does not need to include

the complete class definition but requires that the class is

available when needed.

Objects to be stored and retrieved frequently refer to other

objects. Those other objects must be stored and retrieved at

the same time to maintain the relationships between the

objects. When an object is stored all of the objects that are

reachable from that object are stored as well.

The goals for serializing Java objects are to:

Have a simple yet extensible mechanism.

Maintain the Java object type and safety properties in

the serialized form.

Be extensible to support marshaling and unmarshaling

as needed for remote objects.

Be extensible to support persistence of Java objects.

Require per class implementation only for

customization.

Writing Objects to a Stream

Writing objects and primitives to a stream is a straight

forward process. For example:

// Serialize today's date to a file.

FileOutputStream f = new FileOutputStream("tmp");

ObjectOutput s = new ObjectOutputStream(f);

s.writeObject("Today");

s.writeObject(new Date());

s.flush();

First an OutputStream, in this case a

FileOutputStream, is needed to receive the bytes.

Then an ObjectOutputStream is created that writes to

the OutputStream. Next, the string "Today" and a Date

object are written to the stream. More generally, objects

are written with the writeObject method and primitives

are written to the stream with the methods of

DataOutputStream.

The writeObject method serializes the specified object

and traverses its references to other objects in the object

graph recursively to create a complete serialized

representation of the graph. Within a stream, the first

reference to any object results in the object being serialized

and the assignment of a handle to that object. Subsequent

references to that object are encoded as the handle. Using

object handles preserves sharing and circular references

that occur naturally in object graphs. Subsequent references

to an object use only the handle allowing a very compact

representation.

The serialized encoding of an object consists of the object's

class followed by the fields of each class starting with the

highest superclass and ending with the actual class.

For an object to handle its own serialization it must

implement the writeObject method. To maintain the

integrity of the class, this method is private to the class and

can only be called by the serialization at runtime. This

method is invoked when the fields of its class are to be

written; it should write the information needed to

reinitialize the object when it is deserialized.

The default mechanism writes each non-static and

non-transient field to the stream. Each field is written

appropriately depending on its type. The fields are put in a

canonical order so as to be insensitive to the order of

declaration.

Objects of class Class are serialized as the name of the

class and the fingerprint or hash of the interfaces, methods,

and fields of the class. The name allows the class to be

identified during deserialization and the hash of the class

allows it to be verified against the class of the serialized

object. All other normal Java classes are serialized by

writing the encoding of its Class followed by its fields.

ObjectOutput streams can be extended to customize the

information in the stream about classes or to replace

objects to be serialized. Refer to the annotateClass and

replaceObject method descriptions for details.

Reading Objects from a

Stream

Reading an object from a stream is equally straight

forward:

// Deserialize a string and date from a file.

FileInputStream in = new FileInputStream("tmp");

ObjectInputStream s = new ObjectInputStream(in);

String today = (String)s.readObject();

Date date = (Date)s.readObject();

First an InputStream, in this case a

FileInputStream, is needed as the source stream. Then

an ObjectInputStream is created that reads from the

InputStream. Next, the string "Today" and a Date

object are read from the stream. More generally, objects

are read with the readObject method and primitives are

read from the stream with the methods of

DataInputStream.

The readObject method deserializes the specified object

and traverses its references to other objects recursively to

create the complete graph of objects serialized. Objects

read from the stream are type checked as they are assigned.

Reading an object consists of the decoding of the object's

class and the fields of each class starting with the highest

superclass and ending with the actual class.

For an object to handle its own serialization it must

implement the readObject method. To maintain the

integrity of the class, this method is private to the class and

can only be called by the serialization at runtime. This

method is invoked when the fields of its class are to be

read; it should read the information written by

writeObject and make appropriate assignments to the

object's fields. If the state of the object cannot be

completely restored at the time the object is being read, a

validation callback can be requested by calling the

registerValidation method.

The default mechanism reads each non-static and

non-transient field from the stream. Each field is read

appropriately depending on its type. The fields are read in

the same canonical order as when written so as to be

insensitive to the order of declaration.

Objects of class Class are deserialized as the name of the

class and fingerprint. A fingerprint is a hash of the

interfaces, methods, and fields of the class. The

resolveClass method is called to find the class by name

and return its Class object. The hash is computed for the

returned class and compared with the hash of the class

serialized. Deserialization proceeds only if the class

matches. This ensures that the structure of the stream

matches the structure of the class. All other normal Java

classes are deserialized by reading the encoding of its Class

followed by its fields.

ObjectInput streams can be extended to utilize customized

information in the stream about classes or to replace

objects that have been deserialized. Refer to the

resolveClass and resolveObject method

descriptions for details.

Protecting Sensitive

Information

Warning: The current implementation does not

protect the private fields of objects, and object

serialization, therefore, can be used to reveal

private information that must be kept secret. At

JDK 1.1, the implementation will require

programmers to explicitly declare which classes

can be serialized.

When developing a class that provides controlled access to

resources, care must be taken to protect sensitive

information and functions. During deserialization (by

default) the private state of the object is restored. For

example, a file descriptor contains a handle that provides

access to an operating system resource. Being able to forge

a file descriptor would allow some forms of illegal access,

since restoring state is done from a stream. Therefore, the

serializing runtime must take the conservative approach

and not trust the stream to contain only valid

representations of objects. To avoid compromising a class,

the sensitive state of an object must not be restored from

the stream or it must be reverified by the class. Several

techniques are available to protect sensitive data in classes.

The easiest technique is to mark fields that contain

sensitive data as "private transient". Transient and static

fields are not serialized or deserialized. Simply marking

the field will prevent the state from appearing in the stream

and from being restored during deserialization. Since

writing and reading (of private fields) cannot be superceded

outside of the class, the class's transient fields are safe.

Particularly sensitive classes should not be serialized at all.

To accomplish this, writeObject and readObject

methods should be implemented to throw the

NoAccessException. Throwing an exception will abort

the entire serialization or deserialization process before any

state from the class can be serialized or deserialized.

Some classes may find it beneficial to allow writing and

reading but specifically handle and revalidate the state as it

is deserialized. The class should implement

writeObject and readObject methods to save and

restore only the appropriate state. If access should be

denied, throwing a NoAccessException will prevent

further access.

Fingerprints of Classes

Within an object stream classes are represented by name

and fingerprint. This fingerprint is used to verify that the

class used to deserialize the object is the same as the class

of the object serialized. The shallow signature or

fingerprint of a class is computed by hashing the class

name and access flags, the interfaces supported by the

class, the field names, access flags and signatures, and the

method names, access flags and signatures. Each set of

interfaces, fields, and methods are put in a canonical order

prior to hashing so that the order of declaration does not

affect the hash. The shallow fingerprints of the class and all

superclasses are rehashed to define the fingerprint of the

class that is used in the stream.

The FingerPrintClass implementation also provides a

total fingerprint that includes the fingerprints of each class

referred to by the class as a parameter or return value.

The values and strings included in the hash are those of the

Java Virtual Machine Specification that define classes,

methods, and fields.

Secure Hash Stream

The SHAOutputStream provides an implementation of the

National Institute of Standards and Technology (NIST)

Secure Hash Algorithm (SHA). Its output is a 160-bit (20

byte) secure hash of the bytes written.

// This shows the use of the Java Serializable interface to provide the

function

// of a file of records of different types.

import java.io.*;

class RecordIO

{

static public void main(String args[]) throws Exception

{

ObjectOutputStream out=

new ObjectOutputStream(new FileOutputStream("temp.bin"));

ObjectInputStream in=

new ObjectInputStream(new FileInputStream("temp.bin"));

Employe joe=new Employe("Joe Smith",25,30.5);

Employee sarah=new Employee("Sarah Jones",31,38.3,"Morgan");

Employe bill=new Employe("Bill Brown",45,40.5);

Object o;

out.writeObject(joe);

out.writeObject(sarah);

out.writeObject(bill);

for(int i=0;i<3;i++)

{

o=in.readObject(); // We don't know what type it is

System.out.print(((Employe)o).name+", "+((Employe)o).age);

if(o instanceof Employee)

System.out.print(", nee "+((Employee)o).maidenname);

System.out.println();

}

}

}

class Employe implements Serializable

{

public String name;

public int age;

double salary;

public Employe(String n,int a,double s)

{

name=n;

age=a;

salary=s;

}

}

class Employee extends Employe // This is a female employe

{

public String maidenname;

public Employee(String n,int a,double s, String mn)

{

super(n,a,s);

maidenname=mn;

}

}

How do I unsubscribe?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I unsubscribe?

Date: Fri, 5 Feb 1999 15:51:37 -0500

If you ever want to remove yourself from this mailing list,

you can send mail to <majordomo@vinny.bridgeport.edu> with the following

command in the body of your email message:

unsubscribe cs410x-list

How do I nest layouts in panels?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I nest layouts in panels?

Date: Thu, 11 Feb 1999 13:38:33 -0500

The following example shows

how to nest layouts in panels. Note that

each panel has its own layout manager.

Also note that the pack method is only available

in the fram (not the panel). Pack is required

because it resizes the window to its preferred

size. Frame extends window, but panel does not.

Further only window has the pack method.

Finally, the pack method called addNotify,

which causes all the components in the container

hierarchy to be created.

import java.awt.*;

public class PapPanel extends

Panel {

CpuPanel

cpuPanels[];

PapPanel(

int numberOfCPUs) {

cpuPanels =

new CpuPanel[numberOfCPUs];

setLayout(

new GridLayout(4,5));

for (int i=0;

i < numberOfCPUs; i++) {

cpuPanels[i]=new CpuPanel(i);

add(cpuPanels[i]);

}

}

}

public class Display extends

Frame {

public CpuPanel[]

addCpus(int N) {

setLayout(new

GridLayout(2,1));

PapPanel pap =

new PapPanel(N);

add (pap);

add (new BCP());

pack();

return pap.cpuPanels;

}

public static void main(String args[]) {

System.out.println( "Hello World!" );

Display d = new Display();

CpuPanel cpus[]=d.addCpus(20);

d.setVisible(true);

for (int i =0; i<cpus.length;i++) {

cpus[i].setSpeed(i*2+1);

}

d.repaint();

try {

System.in.read(); // prevent console window from

going away

} catch (java.io.IOException e) {}

}

}

public class BCP

extends Panel {

BCP() {

setLayout(

new GridLayout(1,2));

add(new Button("update"));

add(new

Button("Terminate"));

}

}

public class CpuPanel

extends Panel {

Label speedLabel =

new Label(" 0");

CpuPanel(int cpuNumber) {

setLayout(new

GridLayout(2,1));

add(speedLabel);

add(new Label

("CPU "+cpuNumber));

}

public void setSpeed(float speed) {

speedLabel

= new Label(speed+"");

}

}

How do I check my mail with Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I check my mail with Java?

Date: Thu, 12 Nov 1998 09:27:58 -0400

package net;

import java.applet.*;

import java.awt.*;

import java.net.*;

import java.applet.*;

import java.io.*;

import java.util.Date;

import gui.ClosableFrame;

/**

* The applet.

*/

public class CheckMail extends Applet

{

String serverHostName = null;

boolean standalone = false;

int popPort = 110;

Socket socket;

PrintStream ps;

DataInputStream dis;

InetAddress rina;

InetAddress lina;

CheckMailForm form;

/**

* Initialize the applet.

*/

public void init()

{

form = new CheckMailForm(this);

add(form);

form.resize(300, 300);

setBackground(Color.blue);

if (serverHostName == null) serverHostName =

getCodeBase().getHost();

}

/**

* Show status text to the user.

*/

public void showStatus(String s)

{

System.out.println(s);

if (standalone) return;

super.showStatus(s);

}

/**

* Perform check for e-mail.

*/

public void checkForMail()

throws IOException, NumberFormatException, Exception

{

showStatus("Checking for mail on " + serverHostName);

// Open connection

socket = new Socket(serverHostName, popPort);

String rs;

try

{

rina = socket.getInetAddress();

lina = rina.getLocalHost();

ps = new PrintStream(socket.getOutputStream());

dis = new DataInputStream(socket.getInputStream());

// Check for messages

sendline("USER " + form.getId());

rs = sendline("PASS " + form.getPswd());

if (rs.charAt(0) != '+') throw new

Exception("Incorrect password");

rs = sendline("STAT");

}

catch (Exception ex)

{

socket.close();

throw ex;

}

// Close connection

socket.close();

// Parse result

int r = 0;

r = Integer.parseInt(rs.substring(4, rs.indexOf(" messages")));

// Update result field

form.resultField.setText(Integer.toString(r));

}

/**

* Send a line of data to the server, and return the handshake.

*/

String sendline(String data)

throws IOException

{

System.out.println("sendline out:" + data);

ps.println(data);

ps.flush();

String s = dis.readLine();

System.out.println("sendline in:" + s);

return s;

}

/**

* Main routine, for running as a standalone application.

*/

public static void main(String args[])

{

CheckMail ap = new CheckMail();

ap.serverHostName = "mail.snet.net";

ap.standalone = true;

ClosableFrame fr = new ClosableFrame("CheckMail");

ap.init();

fr.add("Center", ap);

fr.resize(300, 300);

fr.show();

ap.start();

}

}

/**

* Form for obtaining e-mail user id and password from the user.

*/

class CheckMailForm extends Panel

{

CheckMail applet;

// The form's elements...

Label idLabel;

TextField idField;

Label pswdLabel;

TextField pswdField;

Button button;

Label resultLabel;

TextField resultField;

/**

* The constructor.

*/

public CheckMailForm(CheckMail ap)

{

applet = ap;

setBackground(Color.blue);

setLayout(new GridLayout(7, 1));

// Instantiate all the elements, and add them to the form...

add(button = new Button("Check For Mail"));

add(idLabel = new Label("Id:"));

add(idField = new TextField(20));

add(pswdLabel = new Label("Password:"));

add(pswdField = new TextField(20));

pswdField.setEchoCharacter('*');

add(resultLabel = new Label("Messages Waiting:"));

add(resultField = new TextField(6));

resultField.setEditable(false);

// Set the size of the form

resize(250, 250);

}

/**

* Return the value of the ID field in the form.

*/

public String getId()

{

return idField.getText();

}

/**

* Return the value of the password field in the form.

*/

public String getPswd()

{

return pswdField.getText();

}

/**

* Respond to the button click event: check for messages.

*/

public boolean handleEvent(Event e)

{

if ((e.target == button) && (e.id == Event.ACTION_EVENT))

{

try {applet.checkForMail();}

catch (Exception ex)

{

applet.showStatus("Error; unable to check

for messages:\n "

+ ex.toString());

return true;

}

applet.showStatus("Completed.");

return true;

}

return super.handleEvent(e);

}

}

How do I get an address from a name in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I get an address from a name in Java?

Date: Thu, 12 Nov 1998 09:27:58 -0400

package net;

import java.applet.Applet;

import java.awt.*;

import java.net.*;

import java.io.*;

public class SearchDNS extends Applet {

//--------------------------------------------------------------

TextField searchField;

//--------------------------------------------------------------

public void init() {

Label title = new Label(

"Enter a name to get an IP address");

title.setFont(

new Font("Helvetica", Font.BOLD, 18));

title.setBackground(Color.red);

title.setForeground(Color.yellow);

add(title);

add(new Button("Use DNS"));

searchField = new TextField(20);

add(searchField);

}

//--------------------------------------------------------------

// Events from *either* Button or TextField should trigger this.

public boolean action(Event event, Object object)

{

String searchString = searchField.getText();

if (searchString.equals(""))

searchString = "cse.bridgeport.edu";

try { DNS.getName(searchString);}

catch (Exception e) {};

return(true);

}

}

How to I read and Write a gzipped file of floats?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How to I read and Write a gzipped file of floats?

Date: Sun, 22 Nov 1998 09:47:29 -0400

Hi All,

Here is how to read and write a gzipped file of

floats. To test this class, please place it in the gui

package of Kahindu and run

gui.MatFloat (which has its own main).

Please take some time to look this over...

Thanks!

- DL

package gui;

import java.io.*;

import java.awt.*;

import java.util.zip.*;

public class MatFloat extends

Mat {

float f[][];

MatFloat (float flt[][]) {

f = flt;

}

public String getSaveFileName(String prompt) {

FileDialog fd = new

FileDialog(

new Frame(),

prompt,

FileDialog.SAVE);

fd.setVisible(true);

fd.setVisible(false);

String fn=fd.getDirectory()+fd.getFile();

if (fd.getFile() == null) return null; //usr canceled

return fn;

}

public static void main(String args[]) {

System.out.println("Test");

float flt[][] =

{

{1.0f,3.0f,4.0f},

{1.0f,3.0f,4.0f},

{1.0f,3.0f,4.0f}

};

MatFloat mf = new MatFloat(flt);

print(flt);

String fn = mf.getSaveFileName("flt.gz file");

mf.saveAsgz(fn);

mf.readAsgz(fn);

print(mf.f);

}

public void saveAsgz() {

saveAsgz(

getSaveFileName("flt.gz file"));

}

public void saveAsgz(String fn) {

try {

FileOutputStream fos = new FileOutputStream(fn);

GZIPOutputStream gos = new GZIPOutputStream(fos);

ObjectOutputStream oos = new ObjectOutputStream(gos);

oos.writeInt(f.length);

oos.writeInt(f[0].length);

for (int x=0; x < f.length; x++)

for (int y=0; y < f.length; y++)

oos.writeFloat(f[x][y]);

oos.close();

gos.finish();

} catch(Exception e) {

System.out.println("Save saveAsFloatgz:"+e);

}

}

private void readAsgz(String fn) {

try {

FileInputStream fis = new FileInputStream(fn);

GZIPInputStream gis = new GZIPInputStream(fis);

ObjectInputStream ois = new ObjectInputStream(gis);

int w = ois.readInt();

int h = ois.readInt();

f = new float[w][h];

for (int x=0; x < w; x++)

for (int y=0; y < h; y++)

f[x][y] = ois.readFloat();

ois.close();

} catch(Exception e) {

System.out.println("readAsgz:"+e);

}

}

}

How do I do a client server with sockets in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I do a client server with sockets in Java?

Date: Sun, 22 Nov 1998 09:47:29 -0400

import java.io.*;

import java.net.*;

// To run issue 'start java Server' which will set the server listening on

port 1234

// Then issue 'java Client' from the original session

class Server

{

public static void main(String[] args)

{

System.out.println("Starting Server listening on 1234 ...");

try

{

ServerSocket ss= new ServerSocket(1234);

Socket s = ss.accept();

PrintStream out = new PrintStream(s.getOutputStream());

out.println("Server Connected");

s.close();

}

catch (Exception e) { System.out.println(e); }

}

}

class Client

{

public static void main(String[] args)

{

System.out.println("Client Looking...");

try

{

Socket s = new Socket(InetAddress.getLocalHost(),1234);

DataInputStream in = new DataInputStream(s.getInputStream());

System.out.println(in.readLine());

}

catch (Exception e)

{

System.out.println(e);

}

System.out.println("Done.");

}

}

How do I set up for browsing?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I set up for browsing?

Date: Tue, 24 Nov 1998 09:12:49 -0400

There are several reasons for this.

1. Location: Place the html and jar files in the .public_html

directory.

check:

http://www.bridgeport.edu/~yourUid/kahindu.html

http://www.bridgeport.edu/~lyon/kahindu.html

2. Make sure the files are read accessable.

3. Make an applet from the main...

>I can browse the kahindu applet using netscape in local computer. But when

>I put it in my directory, I can't browse it from internet.

>Why?

>

>

>xwan

How do I make a Jar file from many directories?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I make a Jar file from many directories?

Date: Tue, 24 Nov 1998 09:12:49 -0400

The frame hierarchy of Kahindu is such that

a single invocation of

jar cvf classes.jar Main.class fft/*.class gui/*.class

htmlconverter/*.class idx

/*.class vs/*.class

should make a classes.jar file for you...

- DL

>Sir, I can't understand the frame hierachy of your kahindu program fully,

>so I

>have trouble in the homework. I can't init the applet correctly.

>could you give me some kind of suggestions?

>Thank you !

>

>xwan

How do I build a command line Interpreter?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I build a command line Interpreter?

Date: Wed, 25 Nov 1998 08:47:28 -0400

import java.io.*;

import java.util.*;

class Foo {

public void run() {

System.out.println(

"Foo reporting for duty");

}

}

public class TrivialApplication {

static String cn = "Foo";

public static void main(

String args[]) {

String ds =

"1.00001a";

try {

String line;

DataInputStream dis

= new DataInputStream(System.in);

while ((line=dis.readLine())

!= null) {

//System.out.println(line);

StringTokenizer st

= new StringTokenizer

(line);

int tokNum = 0;

while (st.hasMoreTokens() ) {

String

toks = st.nextToken();

//System.out.println(

// toks);

tokNum++;

if (tokNum == 1) {

try {

Object o =

Class.forName(toks).newInstance();

}

catch (ClassNotFoundException e) {

System.out.println(e);

}

}

}

}

}

catch(Exception e) {

System.out.println(e);

}

String line;

try {

Foo a =

(Foo)Class.forName(cn).newInstance();

a.run();

}

catch (Exception e) {

System.out.println(

e);

}

System.out.println( "Hello World!" );

try {

System.in.read(); // prevent console window from

going away

} catch (java.io.IOException e) {}

}

}

How do I tell the type of an object

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I tell the type of an object

Date: Mon, 30 Nov 1998 09:55:32 -0400

When a reference is returned you may cast

it to an instance of the Class type:

Object o = v.elementAt(2);

Class c = o.getClass();

String typeString =

c.getName();

TypeString contains a string description of the class

name.

- DL

> Hi! Professor: Is there anyway to know the exact data type of

>the objects stored in a vector? Such as, whether the element is of type

>String, Double or something else?

>

> Ming

How do I hand in Late homework?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I hand in Late homework?

Date: Thu, 1 Oct 1998 05:58:29 -0500

You can fax it;

You can e-mail it.

If you slip it under a door, you must get a faculty or

staff member to sign and date it.

A time-stamp is required to document when a homework

is handed in.

Regards,

- DL

>Date: Wed, 30 Sep 1998 15:58:00 -0400

>From: Rajendra Maharjan <rajendra@bridgeport.edu>

>X-Accept-Language: en

>MIME-Version: 1.0

>To: lyon@snet.net

>Subject: submit homework # 3

>

>Hi professor,

> I am looking for you from morning to submit homework # 3 of CS 410.

>Since you are not in the office, I slide the paper under your office

>door.

>thank you

>

>Rajendra Maharjan

>

>--

>Rajendra maharjan

>80 University Ave, # 248

>Bridgeport, CT 06604

>phone # 203) 576-2133

>e-mail: rajendra@bridgeport.edu

>URL: http://www.bridgeport.edu/~rajendra

>

How do I set the pict file type?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I set the pict file type?

Date: Sat, 3 Oct 1998 10:05:33 -0500

Hi Al,

The below code is interesting,

but I think that it is not going to work

at all on windows....

- DL

>Dr Lyon,

>I modified FrameGrab's toFile(fn) method with the MRJ Toolkit API so

>that it makes a simpletext pict. Now you wont have to drag the file onto

>your cute little "make Simpletext" program.

>I dunno what they would do in windoze.

>code follows

>cheers

>allan

>

>

>

>// Copyright 1998, Prof. D. Lyon

>//

>import java.awt.*;

>import quicktime.qd.*;

>import quicktime.*;

>import quicktime.std.StdQTConstants;

>import quicktime.std.sg.*;

>import quicktime.app.image.*;

>import com.apple.mrj.*;

>import java.io.*;

>public class FrameGrab

> implements

> StdQTConstants {

>

> public static void main (String args[]) {

> FrameGrab fg = new FrameGrab();

> fg.snapShot();

> System.out.println("click");

> }

>

> private SequenceGrabber sg;

>

> public static Image pictToImage(Pict inPict) {

> ImageData id = null;

> try {

> id.fromPict(inPict);

> } catch (Exception e) {

> System.out.println(e);

> };

> QDRect r = id.getDisplayBounds();

> Image i = null;

> try {

> i =

>

>Toolkit.getDefaultToolkit().createImage(new

> QTImageProducer(

> id, new

> Dimension(

> r.getWidth(),

>r.getHeight())));

>

> }

> catch (Exception e) {

> System.out.println(e);

> }

> return i;

> }

>

> public void toFile() {

> FileDialog fd = new FileDialog(

> new Frame(),

> "Gimme a pict name",

> FileDialog.SAVE);

> fd.show();

>

> String fn= fd.getDirectory()+fd.getFile();

> System.out.println(fn);

> toFile(fn);

> }

> public void toFile(String fn) {

> MRJOSType newType = new MRJOSType("PICT");

> MRJOSType newCreator = new MRJOSType("ttxt");

> MRJFileUtils.setDefaultFileType(newType);

> MRJFileUtils.setDefaultFileCreator(newCreator);

> File file =

> new File(fn);

> Pict p = getPict();

> try {

> p.writeToFile(file);

> }

> catch (Exception e) {

> System.out.println(e);

> };

> }

> public Image getImage() {

> return pictToImage(getPict());

> }

> public Pict getPict() {

> try {

> sg = new SequenceGrabber();

> }

> catch (Exception e) {

> System.out.println(e);

> };

> int offScreenDepth=8;

> int grabPictFlags =

> seqGrabToMemory |

> seqGrabPreview |

> seqGrabRecord |

> seqGrabPlayDuringRecord ;

> QDRect bounds=new QDRect(256,256);

> Pict p = null;

> try {

> p = Pict.fromSequenceGrabber(

> sg,

> bounds,

> offScreenDepth,

> grabPictFlags);

> }

> catch (Exception e) {};

>

> return p;

> }

> private void snapShot() {

> try{

> QTSession.open();

> toFile();

> } catch (Exception ee) {

> ee.printStackTrace();

> QTSession.close();

> }

> }

>

>}

How do I use Gridbag Layout?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I use Gridbag Layout?

Date: Mon, 5 Oct 1998 06:09:16 -0500

The GridBag Layout has one constructor GridBagLayout(). The real trick to

GridBag Layout control is the GridBagConstraints class. The actual

GridBagLayout is in init().

import java.applet.*;

import java.awt.*;

public class Car extends Applet implements Runnable

{

// All the Stuff needed for this Example

Thread m_Car = null;

// Line

private Canvas can = new Canvas();

// plan control

private boolean plan = true;

// components

private Label title1 = new Label("Personal Information",Label.CENTER);

private double f0 = 100.0;

// last

private Label l1 = new Label("Last Name",Label.CENTER);

private TextField t1 = new TextField("",20);

// first

private Label l2 = new Label("First Name",Label.CENTER);

private TextField t2 = new TextField("",20);

// age

private Label lg1 = new Label("Check Your Age",Label.CENTER);

private CheckboxGroup g1 = new CheckboxGroup();

private Checkbox g11 = new Checkbox("16-18",g1,false);

private Checkbox g12 = new Checkbox("19-21",g1,false);

private Checkbox g13 = new Checkbox("22-24",g1,false);

private Checkbox g14 = new Checkbox("25-44",g1,false);

private Checkbox g15 = new Checkbox("45-59",g1,false);

private Checkbox g16 = new Checkbox("Over 60",g1,false);

private double f1 = 0;

// married

private Label lg2 = new Label("Check Your Status",Label.CENTER);

private CheckboxGroup g2 = new CheckboxGroup();

private Checkbox g21 = new Checkbox("Single",g2,false);

private Checkbox g22 = new Checkbox("Married",g2,false);

private Checkbox g23 = new Checkbox("Divorced/Seperated",g2,false);

private double f2 = 0;

// Driving Record

private Label lg3 = new Label("Check Below For Record",Label.CENTER);

private Checkbox g31 = new Checkbox("Check for Accident in last

Four Years");

private double f3 = 0;

private Checkbox g32 = new Checkbox("Check for Traffic Ticket Last

five years");

private double f4 = 0;

// Car Type

private Label lg4 = new Label("Check Your Car Type",Label.CENTER);

private CheckboxGroup g4 = new CheckboxGroup();

private Checkbox g41 = new Checkbox("Standard",g4,true);

private Checkbox g42 = new Checkbox("Intermediate (i)",g4,false);

private Checkbox g43 = new Checkbox("High Performance (h)",g4,false);

private Checkbox g44 = new Checkbox("Sports Model (s)",g4,false);

private Checkbox g45 = new Checkbox("Premium Sports (p)",g4,false);

private double f5 = 0;

// Mile

private Label lg5 = new Label("Miles on Car",Label.CENTER);

private TextField t5 = new TextField("",10);

private double f6 = 0;

// Year

private Label lg6 = new Label("Car Year (two digits please ie

69,96,...)",Label.CENTER);

private TextField t6 = new TextField("",10);

private double f7 = 0;

// Plans

private Button b1 = new Button("Next Plan");

private Button b2 = new Button("Plan B");

// BI/PD

private Label lg7 = new Label("Combined (BI/PD)",Label.CENTER);

private TextField t7 = new TextField("",10);

private Label lg8 = new Label("Each Accid.",Label.CENTER);

private TextField t8 = new TextField("",10);

// Medical

private Label lg9 = new Label("Medical Payments",Label.CENTER);

private TextField t9 = new TextField("",10);

private Label lg10 = new Label("Each Person",Label.CENTER);

private TextField t10 = new TextField("",10);

// Comp

private Label lg11 = new Label("Comprehensive",Label.CENTER);

private TextField t11 = new TextField("",10);

private Label lg12 = new Label("Deductible",Label.CENTER);

private TextField t12 = new TextField("",10);

// Coll

private Label lg13 = new Label("Collision",Label.CENTER);

private TextField t13 = new TextField("",10);

private Label lg14 = new Label("Deductible",Label.CENTER);

private TextField t14 = new TextField("",10);

// Premium

private Label lg15 = new Label("Premium",Label.CENTER);

private TextField t15 = new TextField("",10);

///////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////

// START HERE

public void init()

{

resize(600, 1000);

setBackground(new Color(0x99,0x55,0x99));

// THIS IS HOW TO DECLARE ONE

GridBagLayout gridBag = new GridBagLayout();

GridBagConstraints c = new GridBagConstraints();

// THIS IS HOW TO ACTIVATE ONE

setLayout(gridBag);

// THESE Set a proportional space between components

// These should always be greater than zero unless you want

// Your components to crowd together

// Sun Microsystems suggest you set this at 100 and leave it

c.weightx = 1;

c.weighty = 1;

Font f = new Font("Helvetica",Font.BOLD,15);

// Set Canvas for Line

can.resize(600,5);

can.setBackground(Color.black);

// Header

// THIS IS HOW YOU PLACE A COMPONENT

// The gridx Sets the x position of the Component

// The gridy Sets the y postion of the Component

// The gridwidth Sets the number of columns this Component

will Span

// The gridheight Sets the number of rows this component

will span

c.gridx = 0;

c.gridy = 0;

c.gridwidth = 6;

c.gridheight = 1;

// The anchor is used when a Component is smaller than the space (grid)

// being occupied by the Component

// It has the Following Values:

// CENTER -- the default Note: ALL UPPER CASE !

// NORTH

// NORTHEAST

// EAST

// SOUTHEAST

// SOUTH

// SOUTHWEST

// WEST

// NORTHWEST

c.anchor = GridBagConstraints.CENTER; // Example of

GridBagConstraints.anchor

// When all the Constriants are set then declare the Component

// using these Constriants

gridBag.setConstraints(title1,c); // Example of Setting

Canvas Component to Constraints

title1.setFont(f); // Since Canvas is a

Component you may use the setFont method

// Finally add it to the Container -- in this case The Applet's

Panel (Parent)

add(title1);

// The rest of the Componets are attached the same way

// last name

c.gridx = 0;

c.gridy = 1;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(l1,c);

l1.setFont(f);

add(l1);

c.gridx = 0;

c.gridy = 2;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(t1,c);

t1.setBackground(Color.white);

t1.setFont(f);

add(t1);

// first name

c.gridx = 0;

c.gridy = 3;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(l2,c);

l2.setFont(f);

add(l2);

c.gridx = 0;

c.gridy = 4;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(t2,c);

t2.setFont(f);

t2.setBackground(Color.white);

add(t2);

// age

c.gridx = 0;

c.gridy = 5;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(lg1,c);

lg1.setFont(f);

add(lg1);

c.gridwidth = 1;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

g11.setFont(f);

g12.setFont(f);

g13.setFont(f);

g14.setFont(f);

g15.setFont(f);

g16.setFont(f);

c.gridx = 1;

c.gridy = 6;

gridBag.setConstraints(g11,c);

add(g11);

c.gridx = 2;

c.gridy = 6;

gridBag.setConstraints(g12,c);

add(g12);

c.gridx = 3;

c.gridy = 6;

gridBag.setConstraints(g13,c);

add(g13);

c.gridx = 4;

c.gridy = 6;

gridBag.setConstraints(g14,c);

add(g14);

c.gridx = 5;

c.gridy = 6;

gridBag.setConstraints(g15,c);

add(g15);

c.gridx = 6;

c.gridy = 6;

gridBag.setConstraints(g16,c);

add(g16);

// married

c.gridx = 0;

c.gridy = 7;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(lg2,c);

lg2.setFont(f);

add(lg2);

c.gridwidth = 1;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

g21.setFont(f);

g22.setFont(f);

g23.setFont(f);

c.gridx = 0;

c.gridy = 8;

c.gridwidth = 2;

gridBag.setConstraints(g21,c);

add(g21);

c.gridx = 2;

c.gridy = 8;

c.gridwidth = 2;

gridBag.setConstraints(g22,c);

add(g22);

c.gridx = 4;

c.gridy = 8;

c.gridwidth = 2;

gridBag.setConstraints(g23,c);

add(g23);

//Driving Record

lg3.setFont(f);

g31.setFont(f);

g32.setFont(f);

c.gridx = 0;

c.gridy = 9;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(lg3,c);

lg3.setFont(f);

add(lg3);

c.anchor = GridBagConstraints.WEST;

c.gridx = 1;

c.gridy = 10;

c.gridwidth = 6;

gridBag.setConstraints(g31,c);

add(g31);

c.gridx = 1;

c.gridy = 11;

c.gridwidth = 6;

gridBag.setConstraints(g32,c);

add(g32);

// Car type

c.gridx = 0;

c.gridy = 12;

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(lg4,c);

lg4.setFont(f);

add(lg4);

c.gridwidth = 6;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

g41.setFont(f);

g42.setFont(f);

g43.setFont(f);

g44.setFont(f);

g45.setFont(f);

c.gridx = 1;

c.gridy = 13;

gridBag.setConstraints(g41,c);

add(g41);

c.gridx = 1;

c.gridy = 14;

gridBag.setConstraints(g42,c);

add(g42);

c.gridx = 1;

c.gridy = 15;

gridBag.setConstraints(g43,c);

add(g43);

c.gridx = 1;

c.gridy = 16;

gridBag.setConstraints(g44,c);

add(g44);

c.gridx = 1;

c.gridy = 17;

gridBag.setConstraints(g45,c);

add(g45);

// Miles

c.gridx = 1;

c.gridy = 18;

c.gridwidth = 1;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

t5.setFont(f);

t5.setBackground(Color.white);

gridBag.setConstraints(t5,c);

t5.setText("0.0");

add(t5);

c.gridx = 2;

c.gridy = 18;

c.gridwidth = 4;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg5,c);

lg5.setFont(f);

add(lg5);

// Year

c.gridx = 1;

c.gridy = 19;

c.gridwidth = 1;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

t6.setFont(f);

t6.setBackground(Color.white);

gridBag.setConstraints(t6,c);

t6.setText("0.0");

add(t6);

c.gridx = 2;

c.gridy = 19;

c.gridwidth = 4;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg6,c);

lg6.setFont(f);

add(lg6);

// Line

c.gridx = 0;

c.gridy = 20;

c.gridwidth = 7;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(can,c);

add(can);

// Plans

c.gridx = 0;

c.gridy = 21;

c.gridwidth = 3;

c.gridheight = 1;

c.anchor = GridBagConstraints.CENTER;

gridBag.setConstraints(b1,c);

b1.setFont(f);

add(b1);

c.gridx = 3;

c.gridy = 21;

gridBag.setConstraints(b2,c);

b2.setFont(f);

//add(b2);

// BI/PD

c.gridx = 0;

c.gridy = 22;

c.gridwidth = 2;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg7,c);

lg7.setFont(f);

add(lg7);

t7.setFont(f);

t7.setBackground(Color.white);

c.gridx = 3;

c.gridy = 22;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t7,c);

add(t7);

c.gridx = 4;

c.gridy = 22;

c.gridwidth = 2;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg8,c);

lg8.setFont(f);

add(lg8);

t8.setFont(f);

t8.setBackground(Color.white);

c.gridx = 6;

c.gridy = 22;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t8,c);

add(t8);

// Medical

c.gridx = 0;

c.gridy = 23;

c.gridwidth = 2;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg9,c);

lg9.setFont(f);

add(lg9);

t9.setFont(f);

t9.setBackground(Color.white);

c.gridx = 3;

c.gridy = 23;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t9,c);

add(t9);

c.gridx = 4;

c.gridy = 23;

c.gridwidth = 2;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg10,c);

lg10.setFont(f);

add(lg10);

t10.setFont(f);

t10.setBackground(Color.white);

c.gridx = 6;

c.gridy = 23;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t10,c);

add(t10);

// Comp

c.gridx = 0;

c.gridy = 24;

c.gridwidth = 2;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg11,c);

lg11.setFont(f);

add(lg11);

t11.setFont(f);

t11.setBackground(Color.white);

c.gridx = 3;

c.gridy = 24;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t11,c);

add(t11);

c.gridx = 4;

c.gridy = 24;

c.gridwidth = 2;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg12,c);

lg12.setFont(f);

add(lg12);

t12.setFont(f);

t12.setBackground(Color.white);

c.gridx = 6;

c.gridy = 24;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t12,c);

add(t12);

// Coll

c.gridx = 0;

c.gridy = 25;

c.gridwidth = 2;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg13,c);

lg13.setFont(f);

add(lg13);

t13.setFont(f);

t13.setBackground(Color.white);

c.gridx = 3;

c.gridy = 25;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t13,c);

add(t13);

c.gridx = 4;

c.gridy = 25;

c.gridwidth = 2;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg14,c);

lg14.setFont(f);

add(lg14);

t14.setFont(f);

t14.setBackground(Color.white);

c.gridx = 6;

c.gridy = 25;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t14,c);

add(t14);

// Premium

c.gridx = 0;

c.gridy = 26;

c.gridwidth = 3;

c.gridheight = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(lg15,c);

lg15.setFont(f);

add(lg15);

t15.setFont(f);

t15.setBackground(Color.white);

c.gridx = 6;

c.gridy = 26;

c.gridwidth = 1;

c.anchor = GridBagConstraints.WEST;

gridBag.setConstraints(t15,c);

add(t15);

display();

} // End init()

}

// GridBagConstraints also has a property called fill

// the GridBagConstraints.fill property adjust how much

// space the Component takes up within the grid

// It has the Following Values

// BOTH // fills the Grid

// HORIZONTAL // Allows the Componet to fill Grid Horizontaly

// VERTICAL // same as above except Vertical control

// NONE // no resizing is done

// There is an alternative to the gridy and gridx properties

// it is called GridBagConstraints.RELATIVE

// this allows you to by pass setting gridx and grid y

// for each componet BUT

// you must declare the last Component in a row with

// GridBagConstraints.REMAINDER

// This works fine but you do give up some control of your Components

------------------------------------------------------------------------

How do I use grid layout?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I use grid layout?

Date: Mon, 5 Oct 1998 06:10:51 -0500

You use Grid Layouts for Rectangular Layouts -- mostly.

The Grid Layout has Two construtors: GridLayout(int rows,int cols) and

GridLayout(int rows,int cols,int hgap,int vgap). Both only allow One

Component per Grid Space

Appet Example

public void init()

{

setLayout(new GridLayout(3,3)); // THE ANSWER

Button button0 = new Button("A");

add(button0);

Button button1 = new Button("A#");

add(button1);

Button button2 = new Button("B");

add(button2);

Button button3 = new Button("C");

add(button3);

Button button4 = new Button("C#");

add(button4);

Button button5 = new Button("D");

add(button5);

Button button6 = new Button("D#");

add(button6);

Button button7 = new Button("E");

add(button7);

Button button8 = new Button("F");

add(button8);

// This works for any Component ie doesn't have to be a Button

}

// see www.nbwarner.com/applets/MusicMaker/index.html

// for an Extended (5,5) Music Key Board

///////////////////////////////////////////////////////

////////////////////////////////////////////////////

//////////////////////////////////////////////////////

// The other constructor makes space between the components

// with hgap (Horizontal) vgap (Vertical)

setLayout(new GridLayout(6,4,4,4)); // THE SECOND ANSWER

Label title1 = new Label("Norms",Label.CENTER);

Label title2 = new Label("Corner",Label.CENTER);

Label title3 = new Label("Calculator",Label.CENTER);

title1.setFont(f1);

title2.setFont(f1);

title3.setFont(f1);

add(title1); // titles

add(title2);

add(display); // number display

add(title3); // and more titles

// buttons

Button button0 = new Button("0");

Button button1 = new Button("1");

Button button2 = new Button("2");

Button button3 = new Button("3");

Button button4 = new Button("4");

Button button5 = new Button("5");

Button button6 = new Button("6");

Button button7 = new Button("7");

Button button8 = new Button("8");

Button button9 = new Button("9");

Button button10 = new Button("+");

Button button11 = new Button("-");

Button button12 = new Button("X");

Button button13 = new Button("/");

Button button14 = new Button("1/x");

Button button15 = new Button("Clear");

Button button16 = new Button(".");

Button button17 = new Button("=");

button0.setFont(f);

button1.setFont(f);

button2.setFont(f);

button3.setFont(f);

button4.setFont(f);

button5.setFont(f);

button6.setFont(f);

button7.setFont(f);

button8.setFont(f);

button9.setFont(f);

button10.setFont(f);

button11.setFont(f);

button12.setFont(f);

button13.setFont(f);

button14.setFont(f);

button15.setFont(f);

button16.setFont(f);

button17.setFont(f);

add(button7);

add(button8);

add(button9);

add(button13);

add(button4);

add(button5);

add(button6);

add(button12);

add(button1);

add(button2);

add(button3);

add(button11);

add(button0);

add(button16);

add(button17);

add(button10);

add(button14);

add(button15);

// GOTO: www.nbwarner.com/applets/applet1.html and see Calculator

// for an Example of GridLayout(x,y,m,n); Constructor

------------------------------------------------------------------------

How do I get the author tag in JavaDoc?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I get the author tag in JavaDoc?

Date: Tue, 6 Oct 1998 07:15:48 -0500

There are some options available for generating

Javadoc within the IDE of Metrowerks.

In the settings, select Javadoc from the linker. Then

uncheck the ignore comment check-box.

- DL

>Hi:

>I could use the see tag in method, but i didn't get any reference in my

>html file. About author tag and version tag i could not see anything on

>html. Do, i have to explicitly write in html file for see tag.

>vinita

How do I find javadoc?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I find javadoc?

Date: Tue, 6 Oct 1998 07:28:29 -0500

For those with a pre-3.0 version of the codeWarrior,

you may use the computers in school or the

javadoc command on your own machines.

Typically, in cases such as Abrar's, I would suggest

an upgrade, or a trip to school. Java doc is

installed on the sun's so you can telnet in to

do this type of work without leaving the apartment...

- DL

>Hi Professor,

> i am using "code worrior 2.1" and the pre-linker option from the

>"target settings" does not have the option "javadoc prelinker" please

>tell me how do i go about the problem. i am waiting for your reply.

>

>Abrar

>

>______________________________________________________

>Get Your Private, Free Email at http://www.hotmail.com

How do I know if a class can be public?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I know if a class can be public?

Date: Tue, 6 Oct 1998 09:43:00 -0500

The answer to this depends on how portable

you want to make your source code.

The very portable answer requires that each

public class reside in a file that has a name

which matches the class name.

Thus:

public class Hello {

...

}

resides in the Hello.java file.

Only one public class is permitted per file....

This is not a Java requirement, but a cross-platform

tool requirement.

When making a single jar file for distribution, it does

not matter.

It also does not have to matter in codewarrior...it is

an option in the compiler...

- DL

>Prof. D.Lyon:

>Can I put more than one public class in one .java file?

>I tried to run some small java program, I have three classes in one

>.java file, when I set all of them in public, it did not work. But when I

>set only one class in public, it is ok. Why? How do you manage them in

>your big 'Kahindu' project?

>

>Thank you for your response!

>

>Regards

>-Lin

How do I make Javadoc work on non-public files?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I make Javadoc work on non-public files?

Date: Thu, 8 Oct 1998 09:40:09 -0500

Hi Jijoung,

Let me see if I can respond to your

e-mail below:

>How are you Professor!

>I am jiyoung an.

>I almost finished java CS410 assignment#4.

>I compiled with JDK1.1.6. I think javadoc1.1.x does not work for documenting

>inner clases.

Yes, this is a feature!

Javadoc1.1.6 which I used didn't work with two of my source

>files which are gui/Cshort.java gui/Doable.java. Other source file's no

>problem. Are these -Cshort.java and Doable.java- inner classes?

No.

>How do I

>make javadoc with these two files?

They are not public. You can change the javadoc flags to

output non-public files, or you can make them public....

For example:

package gui;

interface Doable {

public void doit(double a[]);

}

//goes to:

package gui;

public interface Doable {

public void doit(double a[]);

}

OK?

- DL

>I got 4 source files from you for assignment. Two files work fine. so I put it

>on my web page ( www.bridgeport.edu/~jiyoung/java410.html)

>

>Thanks

>Jiyoung An

How do you set alarms in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do you set alarms in Java?

Date: Thu, 8 Oct 1998 09:56:47 -0500

The easier techniques for doing this are described

in my book. See page 99 for putting a thread

to sleep....It will wake anytime you say...

JNI and Java Direct both permit the invocation

of native methods from Java....

- DL

>Dr. Lyon:

>

>I could not find any kind of alarm or timer class in Java packages. Normally

>in any language we can set an alarm for specific number of msec and install

>an alarm event handler, when the time lapses the OS will interrupt and call

>our event handler. So, I would expect to find a wrapper for this behavior in

>any language, but I cannot find it in Java.

>

>Another question, if a language lacks some functionality it is normally

>allowed to embed some other language or use an OS API (i.e. we can use Win32

>API in Visual Basic). How can I use a Win32 API in Java? Or, how can I load

>dynamic link libraries in Java (since all APIs are exported through DLLs)?

>

>Thank for your help

>Regards

>Alex

How do I draw BNF Diagrams?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I draw BNF Diagrams?

Date: Thu, 8 Oct 1998 09:57:55 -0500

>Date: Mon, 05 Oct 1998 10:27:36 +0100

>From: guyot@cui.unige.ch (Jacques Guyot)

>Subject: Re: BNF Diagrams

>X-Sender: guyot@uni2a.unige.ch

>To: "Dr. Douglas Lyon" <lyon@snet.net>

>MIME-version: 1.0

>

>

>Hello

>

>We are working on new version of HyperGOS,

>you can try this version at:

>

>http://cuiwww.unige.ch/db-research/Enseignement/analyseinfo/DIAG33JAVA/index

>.html

>

>If you have comments or sugestions about this, your are welcome.

>

>Thanks

>

>

>>Dear Jacques,

>>I am very interested in generating BNF expression diagrams using

>>the automated tools used in the

>>BNF Web Club Language. Can you give me a pointer

>>to the tools so that I can generate my own?

>>

>>Thanks!

>>

>>Regards,

>> - Doug Lyon

>

How do I do implicit threading?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I do implicit threading?

Date: Thu, 8 Oct 1998 12:54:25 -0500

Implicit threads are available in the AWT...

just call repaint, after the paint. This will

schedule a call to update in so many

milliseconds....

Try the following code and see:

- DL

import java.awt.*;

import java.awt.image.*;

public class DrawPoints extends Frame {

int xsize,ysize,xcenter,ycenter;

int delay=10;

int numberOfPoints=1000;

Graphics backGC;

Image backBuffer;

int[] starX,starY,starZ;

Color[] grayScale;

public static void main(String args[]) {

DrawPoints f = new DrawPoints();

f.setSize(256,256);

f.show();

f.init();

f.repaint();

}

public void init()

{

//Get screen dimensions

xsize=size().width;

ysize=size().height;

xcenter=xsize/2;

ycenter=ysize/2;

//Init double-buffering

backBuffer = createImage(xsize, ysize);

backGC = backBuffer.getGraphics();

starX=new int[numberOfPoints];

starY=new int[numberOfPoints];

starZ=new int[numberOfPoints];

double theta = 0;

double eps = (1.0/numberOfPoints) * 2*Math.PI;

for (int n=0;n<numberOfPoints;n++) {

starX[n]=(int)

((Math.sin(theta)*xsize*2.0)-xsize/2);

starY[n]=(int)

((Math.cos(theta)*ysize*2.0)-ysize/2);

starZ[n]=(int)

(Math.random()*4095);

theta = theta + eps;

}

//Create grayscale tones

grayScale=new Color[256];

for (int n=0;n<256;n++)

grayScale[255-n]=new Color(n,n,n);

}

public void paint(Graphics g)

{

//Clear screen

backGC.setColor(Color.black);

backGC.fillRect(0,0,xsize,ysize);

for (int n=0;n<numberOfPoints;n++)

{

//Move stars and clip against viewplane

//The back clipping plane and the

// view plane are hard coded

//for optimizing reasons.

// Viewplane=512, backplane=4095

starZ[n]-=50;

if (starZ[n]<512) starZ[n]=4095;

int z=starZ[n];

//Apply perspective projection

int x=(starX[n]<<9)/z+xcenter;

int y=(starY[n]<<9)/z+ycenter;

//Apply dept shading

backGC.setColor(grayScale[z>>4]);

//Draw star

backGC.drawLine(x,y,x,y);

}

//Draw buffer to screen

g.drawImage(backBuffer, 0, 0, this);

repaint(50,0,0,256,256);

}

public void update(Graphics g) {

paint(g);

}

}

How do I buffer output in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I buffer output in Java?

Date: Wed, 21 Oct 1998 08:50:50 -0400

The following code is an example

of buffered output in Java:

import java.io.*;

public class fastout {

public static void main(String args[])

{

FileOutputStream fdout =

new FileOutputStream(FileDescriptor.out);

BufferedOutputStream bos =

new BufferedOutputStream(fdout, 1024);

PrintStream ps =

new PrintStream(bos, false);

System.setOut(ps);

final int N = 100000;

for (int i = 1; i <= N; i++)

System.out.println(i);

ps.close();

}

}

How do you uncompress a Jar file?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do you uncompress a Jar file?

Date: Tue, 15 Sep 1998 05:29:32 -0500

To uncompress a Jar file,

you can use two techniques:

On Solaris use:

comm.jar

devil{lyon}56: jar -xvf comm.jar

extracted: META-INF/MANIFEST.MF

created: javax/

created: javax/comm/

extracted: javax/comm/CommApiVersion.class

...

On a platform with codewarrior, you may use an

application called the "ClassWrangler". Just open

the file with the ClassWrangler, then drag the contents

of the window out to the target folder.

- DL

>Date: Mon, 14 Sep 1998 16:17:42 -0400 (EDT)

>From: Kelvin Chew <kelvin@bridgeport.edu>

>X-Sender: kelvin@devil

>To: "Dr. Douglas Lyon" <lyon@snet.net>

>Subject: Re: CPE471 HW1

>MIME-Version: 1.0

>

>Hi Prof.,

>

>I dragged the jar file into the project window. But as I tried to compile

>it, I got the error message that the zip file "comm.jar" is "compressed,

>and cannot be used", followed by some errors related to the javax package.

>Should I decompress the jar file? How?

>

>I put the three files (comm.jar, win32com.dll and javax.comm.properties)

>under the folder Metrowerks/CodeWarrior/bin. Is that the right way?

>

>Thanks for your help.

>Kelvin

>

>> Hi Kelvin,

>> You must drag the jar file into the project window.

>> Then it should find it.

>> Regards,

>> - DL

>>

>> >Hi Prof.,

>> >

>> >I tried to compile the SimpleWrite code using CodeWarrior under WinNT, and

>> >I got the "package not found" error. Where do I change the classpath (in

>> >what file and folder?) to make the code compiled? Thanks for your help.

>> >

>> >

>> >Yours sincerely,

>> >Kelvin Chew

>>

>>

>>

>

How do I run an application with codewarrior?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I run an application with codewarrior?

Date: Wed, 16 Sep 1998 07:46:32 -0500

To run an application with

codewarrior:

1. Start CodeWarrior.

2. file>New Project ...

Select: Java>application, OK

Type a project name (any name is OK).

3. In the project window, select run.

This will compile and run the TrivialApplication

and print "hello world!".

Good luck!

- DL

>From: "Service" <service@webmeridian.com>

>To: <lyon@snet.net>

>Subject: Fw: Frustrating with Code Warrior 3.0

>Date: Wed, 16 Sep 1998 00:12:00 -0400

>X-MSMail-Priority: Normal

>X-Priority: 3

>MIME-Version: 1.0

>

>

>Hi Dr. Lyon:

>

>It's 12am Wed. and I'm trying out the stupid Metrowerks CodeWarrior 3.0 for

>the first time trying to hand in your HW2 by today if I'm still awake. I

>made a new apps. called TrivialApplication (the default apps. with Hello

>World) and ran it. This is the error I'm getting right from the box:

>

>ERROR: Could not execute TrivialApplication: The system cannot find the

>file specified.

>

>I made a project folder called foo where TrivialApplication is residing and

>have it at c:\foo.

>

>I've no clue what this means. I went to set Java Target as

>TrivialApplication with the extension .java. Do you happen to have any

>clue? I think I need more support on this because this is my first time

>writing a Java stand-alone apps (not applet for I've no problem compiling

>that). By the what are your office hours? I do need your help during the

>late afternoon when I return from work. I will have lots of questions. I

>appreciate your help otherwise I'll be sitting here staring at the stupid

>CodeWarrior.

>

>Frustrating,

>

>Yin Leong

>

How do I add jars to my class path?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I add jars to my class path?

Date: Wed, 16 Sep 1998 07:58:34 -0500

To add a library to your class path, place

the library in a directory (call it Jars if you like),

then modify the classpath variable:

setenv CLASSPATH /home/lyon/jars/comm.jar

setenv CLASSPATH ${CLASSPATH}:/usr/lib/java/lib/

setenv CLASSPATH ${CLASSPATH}:.

If you get an import error, echo the classpath:

devil{lyon}41: echo $CLASSPATH

/home/lyon/jars/comm.jar:/usr/lib/java/lib/:.

Thanks!

- DL

How do I compile diffcad?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I compile diffcad?

Date: Wed, 16 Sep 1998 14:01:03 -0500

To compile the code known as Diffcad

(from the book, Java Digital Signal Processing)

gunzip the sofware and untar into a directory.

Then use javac.

For example:

vinny.bridgeport.edu{lyon}6: javac Diffcad.java

vinny.bridgeport.edu{lyon}7: ls

Diffcad.class VS/ grapher/ images/ observers/

Diffcad.java foo.html gui/ lyon/ solid/

StringUtil/ futils/ htmlconverter/ net/ threads/

vinny.bridgeport.edu{lyon}8: echo $CLASSPATH

/usr/lib/java/lib/classes.zip:.

vinny.bridgeport.edu{lyon}9:

- DL

>Dear Professor Douglas A. Lyon, Ph.D.,

>

>Thank you for your very quickly replay, I downloaded the files where you

>said to me that I can find them. I alsof made a hardcopy of de 2 readme

>files. I restorded the tar-file on my server ( Workstation Digital 433-au).

>I get the diffcad.class file working. but the rest of the class files will

>not work.

> I get the following message : Can't find class -name of classfile -.

>

>I changed the permisions of the sub directories under source, but no change.

>

>I have done I java compiling whit JAVAC, still no change.

>

>What is my problem, should I make I jar-file and change the

>classpath-envoriment.

>

>Can you help me?

>Greetings,

>

>

>Beste Groeten,

> __________________________________________________________________

>| Ind. Renaat GOBBIN |phone: +32-11-26 82 71 |

>| Dept. WNI - Natuurkunde |fax: +32-11-26 82 99 (sekr.) |

>| LUC-Limburgs Universitair Centrum|email: rgobbin@luc.ac.be |

>| Universitaire campus - Gebouw D |url: http://pdnweb.luc.ac.be/|

>| B-3590 Diepenbeek, Belgium |Place office : Room G6 |

>| url: http://www.luc.ac.be/ | |

>|__________________________________|_______________________________|

How do I pack an Array of bytes?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How to I pack an Array of bytes?

Date: Wed, 16 Sep 1998 14:08:32 -0500

To convert an array of int into an array of

bytes, assuming that you only want the least

significant 8 bits in the int array, use:

byte [] int2byte(int ints[]) {

byte b[] = new int[ints.length];

for (int i=0; i < ints.length; i++)

b[i] = (byte)ints[i];

return b;

}

>Dr Lyon,

>Inside the MRJClasses.zip file (which I've unzipped to analyze)

>is sun.io.charToByteMacTEC.class which is a subclass of

>sun.io.charToByteConverter.

>This strikes me as something we want to use to talk to the Turntable.

>Yes?No?

>Allan

How do I playback quicktime movies in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I playback quicktime movies in Java?

Date: Thu, 17 Sep 1998 09:06:41 -0500

> you must use the Java plug-in from Sun to get playback in browsers w/QTJ.

> (it will make your life easier writing applets in other ways, also)

>

> so (i) QTW3.0.2, (ii) QTJ & (iii) Java Plug-in 1.1.2(?) for applet

> playback

>

How do I set the com port?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I set the com port?

Date: Thu, 17 Sep 1998 09:10:07 -0500

To set the com port

from a sun to a mac,

remove the comments from

the line

// if (portId.getName().equals("COM2")) {

and comment out the next line, with the "/dev/a" stuff in it.

The PC uses COM2, the sun uses /dev/a

- DL

How do I copy a file in Java?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I copy a file in Java?

Date: Fri, 18 Sep 1998 07:25:13 -0500

import java.io.*;

public class FileCopy {

public static void copy(String from, String to)

throws IOException

{

FileInputStream fis = null;

FileOutputStream fos = null;

try {

fis = new FileInputStream(from);

fos = new FileOutputStream(to);

final int BUFSIZ = 1024;

byte buf[] = new byte[BUFSIZ];

int len = 0;

while ((len = fis.read(buf)) > 0)

fos.write(buf, 0, len);

}

finally {

if (fis != null)

fis.close();

if (fos != null)

fos.close();

}

}

public static void main(String args[])

{

// do many invalid copy() operations

for (int i = 1; i <= 5000; i++) {

try {

copy("xxx.txt", ".");

}

catch (IOException e) {

}

}

// do a valid operation

try {

copy("xxx.txt", "yyy.txt");

}

catch (IOException e) {

System.err.println(e);

}

}

}

How do I install Java programs on Solaris/win95/winnt?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I install Java programs on Solaris/win95/winnt?

Date: Mon, 21 Sep 1998 09:41:21 -0500

Java check is software that

help check the portability of your Java.

Interestingly, it comes with instructions for installation

on a variety of platforms.

This worth looking at for

an installation of any Java software under JDK.

- DL

Solaris

1.Change the current directory to the directory that contains the

application you wish to examine.

2.Execute the JavaCheck command (from the JavaCheck bin directory):

% mypath/JavaCheck/bin/JavaCheckV

mypath indicates the pathname for the JavaCheck distribution directory.

3.If this doesn't run successfully, unset your CLASSPATH environment

variable and type JavaCheck again:

% unsetenv CLASSPATH

% mypath/JavaCheck/bin/JavaCheckV

Windows NT

1.Double-click the System icon inside the Control Panel. When the System

Properties dialog box opens, place the following variables in the lower

list box, which is labeled User Variables. (Be careful not to change your

system environment variables, which appear in the upper list box.)

JDKHOME C:\JDK1.x.x

JAVACHECKHOME C:\JavaCheck

CLASSPATH .;%JDKHOME%\lib\classes.zip

PATH %PATH%;%JDKHOME%\bin;%JAVACHECKHOME%\bin

These settings assume that you have installed both the JDK and the

JavaCheck on drive C. Substitute the correct version of the JDK you are

using for the JDKHome value JDK1.x.x.

If either the JDK or JavaCheck are installed on a different drive,

substitute that drive's designator wherever it is appropriate.

2.From the Windows Start menu or from the Control Panel, open a console

(MS-DOS-style) window.

3.In the console window, change the current directory to the directory that

contains the application you wish to examine.

4.Execute the JavaCheck command:

JavaCheckV

This will run the visual tool version of JavaCheck.

Windows 95

1.Edit the system's AUTOEXEC.BAT file and add the following environment

variable settings:

set JDKHOME=C:\JDK1.x.x

set JAVACHECKHOME=C:\JavaCheck

set PATH=%PATH%;%JAVACHECKHOME%\bin

These settings assume that you have installed both the JDK and the

JavaCheck on drive C. Substitute the correct version of the JDK you are

using for the JDKHOME value JDK1.x.x.

If either either the JDK or JavaCheck are installed on a different drive,

substitute that drive's designator wherever it is appropriate. 2.Perform

steps 2 through 4 of the instructions listed under Windows NT. 3.If you

encounter an "Out of environment space" error, then you'll need to increase

the size of the environment table. You can do this at the command line

(which is temporary) or by editing a configuration file to make a permanent

change (which requires restarting your computer).

To temporarily increase environment space, enter the following at the DOS

prompt:

command /e:8192

To permanently increase environment space, add the following line to your

CONFIG.SYS file and then restart your system:

shell=command.com /e:8192 /p

Once you've increased the size of the environment table, try running

JavaCheck again.

How do I update codewarrior?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I update codewarrior?

Date: Thu, 24 Sep 1998 05:49:33 -0500

Version 3.1 update for windows is at:

http://www.metrowerks.com/db/updates.qry?function=detail&updates_uid=199

Version 3.1 update for mac is at:

http://www.metrowerks.com/db/updates.qry?function=detail&updates_uid=198

- DL

How do I add features to a class?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I add features to a class?

Date: Fri, 25 Sep 1998 10:05:00 -0500

To add features to a class, you

do not need to modify a class.

The procedure is to extend the class.

Thus, you are to write:

public class ModifierFrame extends ShortCutFrame {

...

}

You print the ModifierFrame...not the ShortCutFrame.

An instance of the ModifierFrame should have the ability to

handle the control and alt character....

One way to approach this problem is by overloading the alt

method.

Regards,

- DL

>Professor, I am still not clear about ypur homework. I am not sure what

>you want us to do. modify your program?

>I run your program kahindu, which already include some keyboard shortcut.

>If to modify your program, do we have to print all the program including

>your program plus modified part for homework?

>

>could you just explain it fully?

>

>Thank you very much!

>

>xwan

How do I find Kahindu?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I find Kahindu?

Date: Fri, 25 Sep 1998 10:05:00 -0500

Kahindu is available from:

ftp://vinny.bridgeport.edu/pub/ipij

- DL

>Hi! Prof.

>

>I am not been able check Kahendu.

>When I click on Kahendu error message appear on screen like:

>

>Netscape is unable to locate the server pub

>The server does not have DNS enty.

>Check the server name in the locatiopn URL and try again.

>

>Now what should I Do?

>

>thanks

>

>shobhna

>

>______________________________________________________

>Get Your Private, Free Email at http://www.hotmail.com

How do you determine a key-code?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do you determine a key-code?

Date: Mon, 28 Sep 1998 13:04:42 -0500

To determine a keycode, just

print the keyevent using System.out.println.

Regards,

- DL

>Could you tell me the ASCII or UNICODE for alt and ctrl?

> I think we need it to do the petriMap function , right?

>

>

>xwan

How do I figure out what modifiers are pressed?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I figure out what modifiers are pressed?

Date: Mon, 28 Sep 1998 21:18:54 -0500

The InputEvent class has several modifier masks you

can use to test for keys:

public abstract class InputEvent extends ComponentEvent {

/**

* The shift key modifier constant.

*/

public static final int SHIFT_MASK = Event.SHIFT_MASK;

/**

* The control key modifier constant.

*/

public static final int CTRL_MASK = Event.CTRL_MASK;

/**

* The meta key modifier constant.

*/

public static final int META_MASK = Event.META_MASK;

/**

* The alt key modifier constant.

*/

public static final int ALT_MASK = Event.ALT_MASK;

/**

* The mouse button1 modifier constant.

*/

public static final int BUTTON1_MASK = 1 << 4;

/**

* The mouse button2 modifier constant.

*/

public static final int BUTTON2_MASK = Event.ALT_MASK;

/**

* The mouse button3 modifier constant.

*/

public static final int BUTTON3_MASK = Event.META_MASK;

When trying to figure out which key does what...

use:

public void keyTyped (KeyEvent e) {

System.out.println(e);

int key = e.getKeyChar();

System.out.println("keycode="+key+

" hex="+ Integer.toString(key,16));

int mods = e.getModifiers();

System.out.println("mods="+mods+

" hex="+ Integer.toString(mods,16)

+" keyText="+e.getKeyText(key));

}

To help...

- DL

>> Hello everyone

>> I was working on the HW3 for java and have designed the petrinet and petri

>> table for implementing the additional Control and Alt keys in the menu.

>> The problem is that when i use the Keypressed method it returns a zero

>> value for both the Control and Alt key. The control key with a

>> combination of another key returns a valid unique int value and hence i

>> can check on the ctrl+key combination. Hence i can check if the control

>> key is pressed if the returned value is withen a specific range or not.

>> But the combination of an Alt key with any other non modifier returns a

>> zero value. So how will i trap or know that an Alt key combination has

>> been pressed.

>> I have also tried the KeyTyped method under the awt events and too returns

>> a zero.

>> thanks

>>

>> Leonard Francis

>> mailto:FrancisL@flexi.com

>>

>>

How can I obtain a consistent keyboard mapping?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How can I obtain a consistent keyboard mapping?

Date: Tue, 29 Sep 1998 04:18:26 -0500

One approach to obtaining a mapping between

keystrokes and the integer value of the

keys is to create an array of strings.

The index into the string is the key number and the

value of the string is the short-cut representation.

For example:

"^-A", should represent control-A

- DL

>Hi Professor,

> I am having some problem with the Alt and Ctrl values.I have used

>e.getKeyChar to fine out the int value of those keys. I used the value from

>the source code but when I execute it gives 0 for both keys. Can u help me

>with

>this.

>

>Rajendra Maharjan

How can I print all the key-event info?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How can I print all the key-event info?

Date: Tue, 29 Sep 1998 04:47:44 -0500

public void keyPressed(KeyEvent evt)

{

System.out.println("KeyPressed, consumed: "+evt.isConsumed()+" src is:

"+evt.getSource()+" id: "+evt.getID()+", code:

"+evt.getKeyCode()+"("+evt.getKeyText(evt.getKeyCode())+"), char:

"+(int)evt.getKeyChar()+", modifiers:

"+evt.getKeyModifiersText(evt.getModifiers()));

How do I get tech-support from Metrowerks?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I get tech-support from Metrowerks?

Date: Wed, 30 Sep 1998 06:12:00 -0500

To get tech support on a metrowerks product

you purchased (and I suggest this only in the case

when I have no idea why things are going wrong)...

Use:

support@metrowerks.com

Be sure to fill out the support form that came

with your product, including the serial number.

Sorry I don't know the answer to the below question.

Perhaps a reinstallation?

- DL

>Hi Dr. Lyon,

>

>I just try to generate document for a simple example by Codewarrior, but

>the error message is:

>

>Link Error : Couldn't find Sun JDK or JRE (see release notes for details)

>

>I have already configure Pre-linker as "JavaDoc Pre-linker". Could you

>tell me how to fix this problem?

>

>Thanks

>Chen

How do I run Java using CGI?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I run Java using CGI?

Date: Wed, 30 Sep 1998 06:59:39 -0500

Try http://www.bridgeport.edu/~lyon/cgi-bin/run.cgi

You all should have access to:

/home/lyon/.public_html/cgi-bin/hello

See if you can get this to work in your home directory.

- DL

In the directory:

/home/lyon/.public_html/cgi-bin

in the file:

run.cgi

Place the following code:

#!/bin/sh

echo Content-type: text/html

echo

echo "<HTML><HEAD>"

echo "<TITLE>Running Java"

echo "</TITLE></HEAD>"

echo "<BODY>"

echo "Java output follows"

echo "<hr>"

echo "<h2><center>"

/usr/local/jdk/bin/java hello

echo "</center></h2>"

echo "<hr>"

echo "</BODY></HTML>"

Then:

chmod +x run.cgi

Make sure that the hello.class file is present:

ls

hello/ run.cgi* sysinfo.cgi*

hello.class run.cgi~* sysinfo.cgi~*

Here is the hello.java class:

public class hello {

public static void main(String args[]) {

for(int i=0; i < 10; i++)

System.out.print(i+" ");

}

}

- DL

>please find attached the file containing the script that you mailed to me.

>i just changed the cat command to uname and so prints either roadrunner,

>egypt, devil, stargazer or whatever machine. i am not too sure both

>suppose this is what you wanted. you can just run it from the command line

>and see it even without a browser.

>/~~~\___/~~~\___/~~~\___/~~~\___/~~~\___/~~~\___/~~~\___/

>computers are very stupid, they can only give you answers

>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>olumide mark adebayo

>contact:-

> 150 marina park street

> apt 227, bridgeport, ct 06604-5616

> 203-576-2027

> olumide@bridgeport.edu

> http://www.bridgeport.edu/~olumide

>

>

>

>

>Content-Type: TEXT/PLAIN; charset=US-ASCII; name="sysinfo.cgi"

>Content-ID: <Pine.GSO.4.04.9809291605370.21472@devil>

>Content-Description: sysinfo.cgi

>Content-Disposition: attachment; filename="sysinfo.cgi"

>

>Attachment converted: RAM Disk:sysinfo.cgi (TEXT/MSIE) (00000013)

How do I design my programs?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I design my programs?

Date: Wed, 30 Sep 1998 07:09:22 -0500

Typically there is more than one way

to design a program. You may use

any technique that works. I only explain those

techniques that I have tried myself.

Let me encourage you to explore the Java

technology to its fullest.

Regards,

- DL

>Hi Dr. Lyon:

>

>Do I have to use Key Mapping at all? You have that class commented out in

>ShortCutFrame.java and hence, I assume we don't need it. I believe it's

>just cosmestic right. I'm just printing the UNICODE using e.getKeyCode() in

>integers. But, I do use IsCTRL() and IsAlt() to trap those UNICODE numbers.

>

>Yin Leong

>

>----------

>From: Dr. Douglas Lyon <lyon@snet.net>

>To: cs410x-list@vinny.bridgeport.edu

>Subject: Does Java give ASCII Keycodes?

>Date: Tuesday, September 29, 1998 5:55 AM

>

>No, Java uses UNICODE.

>To perform this mapping, you may like to consider

>writing a program that generates the Java needed to

>create the array. I suggest this because the

>alternative appears to be to run the program

>and write the mapping by hand.

>

>Regards,

> - DL

>

>>Hi Dr.Lyon:

>>

>>I'm not sure what other students are facing. The following is what I'm

>>finding out:

>>

>>1. When using e.getKeyChar(), v gives 118 and V gives 86 but CTRL-v or

>>CTRL-Shift-v gives 22. I realize that with the CTRL key, the result is 118

>>- 96 = 22. That 96 somehow has to do with CTRL. For e or E gives 101.

>>CTRL-e or CTRL-E gives 5, which is 101 - 96 = 5. Try CTRL-4 (any

>>non-letter) and you'll get 0. Strange!

>>

>>2. As for Alt-c, you get 99 (same as c itself). How the world one can

>>detect Alt? Moreover, when I hit Alt-any non-modifier, the JView hangs up

>>and is not willing to take any keystroke until I move the window focus to

>>the Win 95 desktop and go back into JView window. I'm not sure whether

>this

>>is true in Unix or Mac.

>>

>>3. Now when I use e.getKeyCode(), I cannot get lower case letter at all.

>>Lower case on the keyboard gives upper case in the integer result.

>>Moreover, hitting CTRL-c is now become CTRL (17) and then C (99) - not 3.

>>Why? I prefer using e.getKeyCode() then because I can separately identify

>>the modifier and non-modifier. But, I won't be able to use lower case

>>letter.

>>

>>So should we use e.getKeyCode() or e.getKeyChar()? If we had to use

>>e.getKeyChar(), maybe we would hand in HW3 next year or until Scott

>McNealy

>>(CEO of Sun) figures out how to use ASCII coding.

>>

>>Sincerely,

>>

>>Yin Leong

>>

>>

>>----------

>>From: Xiang Wan <xwan@bridgeport.edu>

>>To: cs410x-list@vinny.bridgeport.edu

>>Subject: Re: FW: Need help

>>Date: Monday, September 28, 1998 3:54 PM

>>

>>changed getKeyChar () to getKeyCode()

>>

>>xwan

How do you account for PEER classes?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do you account for PEER classes?

Date: Wed, 30 Sep 1998 07:13:58 -0500

Peer classes are the interface between the operating

system subroutines and the Java AWT. This

substrate is used to make Java more portable between

platforms. Their implements are left

to large libraries (like x-windows, on a sun) which

give us the Dialog boxes and Frames...

Regards,

- DL

>Dr. Lyon:

>

>I see that almost all visual AWT classes deal with something called peer,

>and there is a peer package where all the classes are repeated but they have

>all but no code. Can you, please, explain what all this peer stuff is about?

>

>Here is an example that you can find in java.awt.Dialog.java:

>

>/**

> * Creates the dialog's peer. The peer allows us to change the

>appearance

> * of the frame without changing its functionality.

> * @since JDK1.0

> */

> public void addNotify() {

> if (peer == null) {

> peer = getToolkit().createDialog(this);

> }

> super.addNotify();

> }

>

>

>Regards

>Alex

How do I describe a problem to get help?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: How do I describe a problem to get help?

Date: Wed, 30 Sep 1998 07:16:28 -0500

In order to describe a problem so that you

can get help, you must include at least some of the

error message...

For example,

"but still having some probelm

>executing it."

Could mean:

1. It does not compile

2. It throws an exception

3. It prints wrong output

4. ....

Without the specific detail, I cannot guess at a solution.

Regards,

- DL

>Hi Prof.

>i'm also having a simliar problem getting the values of Alt and Ctrl.

>i've tried using both e.getKeyChar() and e.getKeyCode but still having

>some probelm

>executing it.

>

>sushil gurung

>

>Rajendra Maharjan wrote:

>

>> Hi Professor,

>> I am having some problem with the Alt and Ctrl values.I have used

>> e.getKeyChar to fine out the int value of those keys. I used the value from

>> the source code but when I execute it gives 0 for both keys. Can u help

>>me with

>> this.

>>

>> Rajendra Maharjan

How do you run a makefile?

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: [CS410X] How do you run a makefile?

Date: Wed, 22 Apr 1998 13:23:28 -0400

One students writes:

>Dear Prof. Lyon,

>

>I have trouble to make it run. I have no idea how to do it?

>

>

>

>jordan% Makefile

>Makefile: Permission denied

To run a make file type:

make

If there is a command in the make, it will appear

in the Makefile itself. For example, in one make file

we see:

>comp: # co $(SRC)

> javac -d ~/classes $(SRC) # rcsclean docs: # co -kv $(SRC)

> chmod u+w $(SRC)

> mv $(SRC) ..

Therefore type:

make comp

This will invoke the javac on the $(SRC) and place

the classes in your ~/classes directory (which must exist!)...

- DL

How to display an image (sequence)

From: "Dr. Douglas Lyon" <lyon@snet.net>

Subject: [CS410X] How to display an image (sequence)

Date: Mon, 16 Mar 1998 07:15:43 -0400

import java.awt.*;

import java.applet.Applet;

import java.net.*;

/*

* This applet displays an image sequence (gif animation)

*/

public class ImageDisplay extends Applet {

Image image;

URL url; // location of the image

public void init() {

try {

url = new URL(

"http://lyon.bridgeport.edu/cpe210/kmaps/k1.gif");

}

catch (MalformedURLException e)

{e.printStackTrace();}

image = getImage(url);

}

public void paint(Graphics g) {

g.drawImage(image, 0, 0, this);

}

}

[CS411X] CS588x Lect 4 Code Example How do I move Components?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 19 Feb 1999 08:07:25 -0500

import java.awt.*;

import java.awt.event.*;

public class Main extends Frame {

CheckboxMenuItem testCB = new CheckboxMenuItem("Test");

Main() {

super("Container Example");

MenuBar mb = new MenuBar();

ActionListener actionListener = new ActionEventHandler();

MouseEventHandler mouseListener = new MouseEventHandler();

// Initialize Edit Menu

Menu m = new Menu("Edit");

m.add("Remove All");

testCB.addItemListener(new ItemEventHandler());

m.add(testCB);

mb.add(m);

m.addActionListener(actionListener);

// Initialize Add Menu

m = new Menu("Add");

m.add("java.awt.Button");

m.add("java.awt.Checkbox");

m.add("java.awt.Choice");

m.add("java.awt.List");

m.add("java.awt.MenuItem");

m.add("java.awt.Scrollbar");

m.add("java.awt.TextArea");

m.add("java.awt.TextField");

m.add("java.awt.Panel");

m.add("OvalComponent");

m.add("RectangleComponent");

m.add("TriangleComponent");

mb.add(m);

// Set the menubar.

setMenuBar(mb);

// Listen for events.

m.addActionListener(actionListener);

addMouseListener(mouseListener);

addMouseMotionListener(mouseListener);

// Remove the default layout manager.

setLayout(null);

setSize(400, 200);

show();

}

Component dragging;

Component stretching;

Point offset;

class MouseEventHandler extends MouseAdapter

implements MouseMotionListener {

public void mousePressed(MouseEvent evt) {

int x = evt.getX();

int y = evt.getY();

Component c = getComponentAt(x, y);

if (c != null && c != Main.this) {

if (evt.isShiftDown() && evt.isControlDown()) {

remove(c);

} else if (evt.isAltDown()) {

stretching = c;

// Bring to front.

remove(c);

add(c, 0);

} else {

offset = new Point(x-c.getLocation().x,

y-c.getLocation().y);

dragging = c;

// Bring to front.

remove(c);

add(c, 0);

repaint();

}

}

}

public void mouseReleased(MouseEvent evt) {

stretching = dragging = null;

}

public void mouseDragged(MouseEvent evt) {

int x = evt.getX();

int y = evt.getY();

if (dragging != null) {

dragging.setLocation(x-offset.x, y-offset.y);

} else if (stretching != null) {

stretching.setSize(x-stretching.getBounds().x,

y-stretching.getBounds().y);

}

}

public void mouseMoved(MouseEvent evt) {

}

}

int newX, newY;

class ActionEventHandler implements ActionListener {

public void actionPerformed(ActionEvent evt) {

newX = Math.max(getInsets().left, newX);

newY = Math.max(getInsets().top, newY);

Component c = null;

String arg = evt.getActionCommand();

try {

Class cl = Class.forName(arg);

c = (Component)cl.newInstance();

add(c);

Dimension d = c.getPreferredSize();

c.setBounds(newX, newY, d.width, d.height);

c.setEnabled(testCB.getState());

newX += 20;

newY += 20;

if (newX > getSize().width*3/4)

newX = 0;

if (newY > getSize().height*3/4)

newY = 0;

}

catch (Exception e) {

//System.out.println(e);

}

repaint();

}

}

class ItemEventHandler implements ItemListener {

public void itemStateChanged(ItemEvent evt) {

Component[] all = getComponents();

boolean newState = (evt.getStateChange() == ItemEvent.SELECTED);

// Enable all the components.

for (int i=0; i<all.length; i++) {

all[i].setEnabled(newState);

}

}

}

static public void main(String[] args) {

System.out.println("hello");

new Main();

}

}

class OvalComponent extends Component

implements FocusListener {

boolean hasFocus;

OvalComponent() {

// Listen for focus events.

addFocusListener(this);

setSize(80, 80);

}

public void paint(Graphics g) {

g.setColor(Color.red);

g.fillOval(0, 0, getSize().width-1, getSize().height-1);

}

public Dimension getPreferredSize() {

return getSize();

}

public boolean isFocusTraversable() {

return true;

}

public boolean contains(int x, int y) {

int midX = getSize().width/2;

int midY = getSize().height/2;

// This formula doesn't really work for ovals.

return (midX-x)*(midX-x) + (midY-y)*(midY-y) <= midX*midX;

}

public void focusGained(FocusEvent evt) {

hasFocus = true;

repaint();

}

public void focusLost(FocusEvent evt) {

hasFocus = false;

repaint();

}

}

class TriangleComponent

extends OvalComponent {

public void paint(Graphics g){

g.setColor(Color.blue);

Polygon p

= new Polygon();

p.addPoint(0,0);

p.addPoint(getSize().width,

0);

p.addPoint(getSize().width/2,

getSize().height);

p.addPoint(0,0);

g.fillPolygon(p);

}

}

class RectangleComponent

extends OvalComponent

implements FocusListener {

public void paint(Graphics g) {

g.setColor(Color.green);

g.fillRect(0, 0, getSize().width-1, getSize().height-1);

}

}

[CS411X] How do I add a couple of panels to a frame?

Dr. Douglas Lyon ( lyon@snet.net)

Thu, 18 Feb 1999 09:44:10 -0500

import java.awt.*;

class ButtonControlPanel

extends Panel {

Button b1 = new

Button("BUY");

Button b2 = new

Button("SELL");

ButtonControlPanel() {

add(b1);

add(b2);

}

}

class PricePanel extends

Panel {

Label l;

public void init(String pcs) {

l = new Label(pcs);

add(l);

setLayout(

new GridLayout(0,1));

}

PricePanel(String pcs) {

init(pcs);

update(pcs);

}

public void update(

String pcs){

l.setText(pcs);

}

}

public class PriceArrayFrame

extends Frame {

PricePanel pp =

new PricePanel(

"aapl,38.75,+1.25");

public void init() {

setLayout(new

GridLayout(0,1,20,30));

add(new PricePanel(

"aapl,38.75,+1.25"));

add(new PricePanel(

"aapl,38.75,+1.25"));

add(new PricePanel(

"aapl,38.75,+1.25"));

add(new PricePanel(

"aapl,38.75,+1.25"));

add(new ButtonControlPanel());

pack();

setVisible(true);

}

public static

void main(

String args[]){

PriceArrayFrame

paf = new

PriceArrayFrame();

paf.init();

}

}

[CS411X] How do I use movable components in an interface?

Dr. Douglas Lyon ( lyon@snet.net)

Wed, 17 Feb 1999 07:08:14 -0500

The following code provides the front-end

for the network of workstations. The new component,

called the RectangleComponent, extends the MovableComponent.

As a result, when the cursor moves over the rectangle,

the shape of the cursor changes and a click and

drag of the mouse enables the user to move the component.

More importantly, the AWT conducts the damage control,

so that only a small area is repainted. This greatly speeds

the interactive feel of the program.

- Doug

import java.awt.*;

import java.awt.event.*;

public class Display extends

ClosableFrame implements

ComponentListener {

public void componentShown(

ComponentEvent e){}

public void componentMoved(

ComponentEvent e){}

public void componentHidden(

ComponentEvent e){}

public void componentResized(

ComponentEvent e){

pack();

}

public CpuPanel[] addCpus(int N) {

setLayout(new

GridLayout(2,1));

setBackground(Color.white);

PapPanel pap =

new PapPanel(N);

add (pap);

add (new BCP(this));

pack();

return pap.cpuPanels;

}

public void incrementCpus() {

for (int i =0; i<cpus.length;i++) {

cpus[i].setSpeed(cpus[i].getSpeed()+1);

cpus[i].setLightOn(true);

}

}

public void terminateCpus() {

for (int i =0; i<cpus.length;i++) {

cpus[i].setSpeed(0);

cpus[i].setLightOn(false);

}

}

CpuPanel cpus[];

public void init() {

cpus=addCpus(20);

for (int i =0; i<cpus.length;i++)

cpus[i].setSpeed(i*2+1);

setVisible(true);

addComponentListener(this);

}

public static void main(String args[]) {

Display d = new Display();

d.init();

}

}

class BCP

extends Panel implements ActionListener {

Button updateButton = new Button("update");

Button terminateButton = new Button("terminate");

Display display;

BCP(Display _display) {

display = _display;

setBackground(Color.white);

add(updateButton);

add(terminateButton);

updateButton.addActionListener(this);

terminateButton.addActionListener(this);

}

public void actionPerformed(ActionEvent e) {

if (e.getSource()==updateButton) {

display.incrementCpus();

return;

}

if (e.getSource()==terminateButton) {

display.terminateCpus();

return;

}

}

}

class CpuControlPanel

extends Panel {

CpuControlPanel() {

setLayout(new GridLayout(0,3));

}

}

class CpuPanel

extends Panel implements ItemListener {

private CpuControlPanel cpucp

= new CpuControlPanel();

private Label speedLabel =

new Label("0");

private Choice cpuInfo

= new Choice();

private RectangleComponent onLight =

new RectangleComponent(false);

private Checkbox cb =

new Checkbox("on",true);

private static

int cpuNumber = 0;

private float speed = 0;

CpuPanel(String cpuName) {

setBackground(Color.white);

cpuNumber++;

setLayout(new GridLayout(0,1));

cpucp.add(onLight);

cpucp.add(cb);

cb.addItemListener(this);

cpucp.add(speedLabel);

cpuInfo.add("CPU:"+cpuNumber);

cpuInfo.add(cpuName);

cpuInfo.setBackground(Color.white);

add(cpucp);

add(cpuInfo);

}

public void setSpeed(float _speed) {

speed = _speed;

speedLabel.setText

(" "+speed);

}

public float getSpeed() {

return speed;

}

public void setLightOn(boolean on) {

onLight.setState(on);

cb.setState(on);

}

void checkboxChanged() {

onLight.setState(cb.getState());

//activate cpu or

//deactivecpu

}

public void itemStateChanged(ItemEvent e) {

if (e.getSource() == cb) {

checkboxChanged();

return;

}

}

}

class PapPanel extends

Panel {

CpuPanel

cpuPanels[];

PapPanel(

int numberOfCPUs) {

cpuPanels =

new CpuPanel[numberOfCPUs];

setBackground(Color.white);

setLayout(

new GridLayout(5,0,10,20));

for (int i=0;

i < numberOfCPUs; i++) {

cpuPanels[i]=

new CpuPanel(

"192.107.38."+(i+20));

add(cpuPanels[i]);

}

}

}

class CircleComponent

extends MovableComponent {

public void paint(Graphics g) {

g.drawOval(

getLocation().x,

getLocation().y,

getSize().width,

getSize().height);

}

}

abstract class MovableComponent

extends Component

implements MouseMotionListener {

private int w=10;

private int h=5;

private boolean initialized = init();

private boolean init() {

addMouseMotionListener(this);

setCursor(

Cursor.getPredefinedCursor(

Cursor.HAND_CURSOR));

return true;

}

public void mouseMoved(

MouseEvent e) {}

public void mouseDragged(

MouseEvent e) {

setLocation(

e.getX(),

e.getY());

}

abstract public void paint(Graphics g);

public Dimension getPreferredSize() {

return new Dimension(w,h);

}

}

class RectangleComponent

extends MovableComponent

implements ActionListener {

private boolean on = true;

public RectangleComponent(boolean state) {

on = state;

addActionListener(this);

}

public void setState(boolean _on) {

on = _on;

repaint();

}

public void paint(Graphics g) {

setBackground(Color.white);

Point pt = getLocation();

Dimension d = getPreferredSize();

if (on)

g.fillRect(pt.x,pt.y,d.width,d.height);

else

g.drawRect(pt.x,pt.y,d.width,d.height);

}

public void actionPerformed(ActionEvent e) {

//do the action thingy,if needed

//repaint();

}

transient ActionListener actionListener;

public synchronized void addActionListener(ActionListener l) {

actionListener = AWTEventMulticaster.add(actionListener, l);

}

public synchronized void removeActionListener(ActionListener l) {

actionListener = AWTEventMulticaster.remove(actionListener, l);

}

class MouseEventHandler extends MouseAdapter {

public void mousePressed(

MouseEvent e) {

if (actionListener != null)

actionListener.actionPerformed(

new ActionEvent(this,

ActionEvent.ACTION_PERFORMED, null));

}

}

}

class ClosableFrame extends Frame

implements WindowListener {

// constructor needed to pass

// window title to class Frame

public ClosableFrame() {

// call java.awt.Frame(String) constructor

super();

setBackground(Color.white);

addWindowListener(this);

}

public void windowClosing(WindowEvent e) {

dispose();

}

public void windowClosed(WindowEvent e) {};

public void windowDeiconified(WindowEvent e) {};

public void windowIconified(WindowEvent e) {};

public void windowActivated(WindowEvent e) {};

public void windowDeactivated(WindowEvent e) {};

public void windowOpened(WindowEvent e) {};

} // end class ClosableFrame

[CS411X] How do I intersect a ray with an ellipse?

Dr. Douglas Lyon ( lyon@snet.net)

Wed, 17 Feb 1999 06:36:19 -0500

Formulate the code by subst'ing the

parametric formula of a ray into that of the

implicit equation for an ellipse. Then solve for the

roots. The resulting code follows:

public Vec2d intersect(Ray2d ray) {

double a=w/2.0;

double b=h/2.0;

double xd=ray.d.v[0];

double yd=ray.d.v[1];

double xp=ray.p.v[0];

double yp=ray.p.v[1];

double deltax = xp-xc;

double deltay = yp-yc;

double b2 = b*b;

double a2 = a*a;

double A=b2*xd*xd+a2*yd*yd;

double B=xp*xd*b2-xc*xd*b2+yp*yd*a2-yc*yd*a2;

double C=deltax*deltax*b2+deltay*deltay*a2-a2*b2;

double sq=B*B-A*C;

// Check if intersects

if (sq<0) return null;

sq=Math.sqrt(sq);

float t1=(float)((-B-sq)/A);

float t2=(float)((-B+sq)/A);

// check if soln behind the ray

if (t2<0 && t1<0) return null;

// if t2 is behind the ray, then t1

if (t2 < 0) return ray.vecOnLine(t1);

// if t1 is behind the ray, then t2

if (t1 < 0) return ray.vecOnLine(t2);

// select the minimum, cause it is closest.

t1 = Math.min(t1,t2);

return ray.vecOnLine(t1);

}

[CS411X] How do I put a gui on my stock quotes?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 16 Feb 1999 10:49:37 -0500

Here is a simple gui for

the stock quotes. Note, this updates every 2 seconds,

but has a 20 minute delay....

- DL

import java.util.Vector;

import java.util.StringTokenizer;

import java.util.Date;

import java.io.InputStreamReader;

import java.io.BufferedReader;

import java.io.IOException;

import java.net.URL;

import java.awt.*;

public class QuoteFrame extends Frame {

Vector quotes = new Vector();

Label labels[];

public void init() {

getQuotes();

setBackground(Color.white);

labels = new Label[quotes.size()];

for (int i=0; i < quotes.size(); i++) {

labels[i] = new Label(

(String)quotes.elementAt(i));

add(labels[i]);

}

setLayout(new GridLayout(0,1,10,10));

pack();

setVisible(true);

}

public void updateDisplay() {

getQuotes();

for (int i=0; i < quotes.size(); i++) {

labels[i].setText(

(String)quotes.elementAt(i));

}

}

public void paint(Graphics g) {

updateDisplay();

repaint(2000);

}

public Vector getQuotes() {

Vector s = new Vector();

s.addElement("aapl");

s.addElement("open");

s.addElement("xlnx");

s.addElement("altr");

s.addElement("mot");

s.addElement("cy");

s.addElement("crus");

s.addElement("mtwkf");

s.addElement("sfa");

s.addElement("adbe");

s.addElement("nn");

s.addElement("msft");

s.addElement("sunw");

return quotes =

Quote.getUrl(

Quote.makeQuoteURLString(s));

}

public static void main(String args[]) {

QuoteFrame qf = new QuoteFrame();

qf.init();

}

}

public class Quote {

public static void main(String args[]) {

Vector s = new Vector();

s.addElement("aapl");

s.addElement("open");

s.addElement("xlnx");

s.addElement("altr");

s.addElement("mot");

s.addElement("cy");

s.addElement("crus");

s.addElement("mtwkf");

s.addElement("sfa");

s.addElement("adbe");

s.addElement("nn");

s.addElement("msft");

s.addElement("sunw");

printVector(

getUrl(

makeQuoteURLString(s)));

}

public static void printVector(Vector v) {

for (int i =0; i < v.size();i++) {

System.out.println(v.elementAt(i));

}

}

public static Vector getUrl(String _URLString) {

Vector contents = new Vector();

BufferedReader in = null;

try {

URL URLString = new URL(_URLString);

in = new BufferedReader(new

InputStreamReader(URLString.openStream()));

String line;

contents.addElement("Copyright 1999 by Doug Lyon

http://www.docjava.com");

contents.addElement("symbol\tprice\tdate\ttime"+

" (20 min. Delay)\t change\t open\t bid\t ask\t volume");

while(null != (line = in.readLine()))

contents.addElement(line);

}

catch (Exception e) {

e.printStackTrace();

}

finally {

try {

if (in != null) in.close();

}

catch (IOException e) {

e.printStackTrace();

}

}

return contents;

}

public static String makeQuoteURLString(Vector symbols) {

String symbolsString = "";

for(int i = 0; i < symbols.size(); i++) {

String symbol = (String)symbols.elementAt(i);

symbolsString += ((i != 0) ? "," : "") + symbol.toUpperCase();

}

return

"http://quote.yahoo.com/download/javasoft.beans?SYMBOLS=" +

symbolsString +

"&format=sl";

}

}

[CS411X] How do I get Stockquotes in Java?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 16 Feb 1999 08:57:18 -0500

Try this:

import java.util.Vector;

import java.util.StringTokenizer;

import java.util.Date;

import java.io.InputStreamReader;

import java.io.BufferedReader;

import java.io.IOException;

import java.net.URL;

public class Quote {

public static void main(String args[]) {

Vector s = new Vector();

s.addElement("aapl");

s.addElement("open");

s.addElement("xlnx");

s.addElement("altr");

s.addElement("mot");

s.addElement("cy");

s.addElement("crus");

s.addElement("mtwkf");

s.addElement("sfa");

s.addElement("adbe");

s.addElement("nn");

s.addElement("msft");

s.addElement("sunw");

Quote.printQuotesFromYahoo(s);

}

static void printQuotesFromYahoo(Vector symbols) {

{

String symbolsString = "";

for(int i = 0; i < symbols.size(); i++) {

String symbol = (String)symbols.elementAt(i);

symbolsString += ((i != 0) ? "," : "") + symbol.toUpperCase();

}

String quoteURLString =

"http://quote.yahoo.com/download/javasoft.beans?SYMBOLS=" +

symbolsString +

"&format=sl";

BufferedReader in = null;

System.out.println("symbol price date time change open bid ask

volume");

try {

URL quoteURL = new URL(quoteURLString);

in = new BufferedReader(new InputStreamReader(quoteURL.openStream()));

String line;

while(null != (line = in.readLine())) {

StringTokenizer t = new StringTokenizer(line, ",\"");

System.out.println(line);

String symbol = t.nextToken();

double price = Double.valueOf(t.nextToken()).doubleValue();

t.nextToken();

Date date = new Date();

t.nextToken();

Date lastTrade = date;

double change = Double.valueOf(t.nextToken()).doubleValue();

double open = Double.valueOf(t.nextToken()).doubleValue();

double bid = Double.valueOf(t.nextToken()).doubleValue();

double ask = Double.valueOf(t.nextToken()).doubleValue();

int volume = Integer.valueOf(t.nextToken()).intValue();

}

}

catch (Exception e) {

e.printStackTrace();

}

finally {

try {

if (in != null) in.close();

}

catch (IOException e) {

e.printStackTrace();

}

}

}

}

}

[CS411X] How do I make a movable component?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 16 Feb 1999 04:59:17 -0500

If you want

a movable component, all you should ever have

to do is implement a MovableComponent class.

This requires an implementation of the paint method...

and an invocation of house-keeping in the super class.

Note how we defined a boolean instance variable, called initialized,

which allows for after-construction house keeping in the

super-class.

- DL

class CircleComponent

extends MovableComponent {

public void paint(Graphics g) {

g.drawOval(

getLocation().x,

getLocation().y,

getSize().width,

getSize().height);

}

}

abstract class MovableComponent

extends Component

implements MouseMotionListener {

private int w=10;

private int h=5;

private boolean initialized = init();

// init does the house keeping during construction

private boolean init() {

addMouseMotionListener(this);

setCursor(

Cursor.getPredefinedCursor(

Cursor.HAND_CURSOR));

return true;

}

public void mouseMoved(

MouseEvent e) {}

public void mouseDragged(

MouseEvent e) {

setLocation(

e.getX(),

e.getY());

}

abstract public void paint(Graphics g);

public Dimension getPreferredSize() {

return new Dimension(w,h);

}

}

[CS411X] How do I nest layouts in panels?

Dr. Douglas Lyon ( lyon@snet.net)

Thu, 11 Feb 1999 13:38:33 -0500

The following example shows

how to nest layouts in panels. Note that

each panel has its own layout manager.

Also note that the pack method is only available

in the fram (not the panel). Pack is required

because it resizes the window to its preferred

size. Frame extends window, but panel does not.

Further only window has the pack method.

Finally, the pack method called addNotify,

which causes all the components in the container

hierarchy to be created.

import java.awt.*;

public class PapPanel extends

Panel {

CpuPanel

cpuPanels[];

PapPanel(

int numberOfCPUs) {

cpuPanels =

new CpuPanel[numberOfCPUs];

setLayout(

new GridLayout(4,5));

for (int i=0;

i < numberOfCPUs; i++) {

cpuPanels[i]=new CpuPanel(i);

add(cpuPanels[i]);

}

}

}

public class Display extends

Frame {

public CpuPanel[]

addCpus(int N) {

setLayout(new

GridLayout(2,1));

PapPanel pap =

new PapPanel(N);

add (pap);

add (new BCP());

pack();

return pap.cpuPanels;

}

public static void main(String args[]) {

System.out.println( "Hello World!" );

Display d = new Display();

CpuPanel cpus[]=d.addCpus(20);

d.setVisible(true);

for (int i =0; i<cpus.length;i++) {

cpus[i].setSpeed(i*2+1);

}

d.repaint();

try {

System.in.read(); // prevent console window from

going away

} catch (java.io.IOException e) {}

}

}

public class BCP

extends Panel {

BCP() {

setLayout(

new GridLayout(1,2));

add(new Button("update"));

add(new

Button("Terminate"));

}

}

public class CpuPanel

extends Panel {

Label speedLabel =

new Label(" 0");

CpuPanel(int cpuNumber) {

setLayout(new

GridLayout(2,1));

add(speedLabel);

add(new Label

("CPU "+cpuNumber));

}

public void setSpeed(float speed) {

speedLabel

= new Label(speed+"");

}

}

[CS411X] How do I intersect a ray with an ellipses?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 5 Feb 1999 09:01:23 -0500

When a ray is given by:

f(t)=P + t D

where P = start point

and D = normalized direction vector

Substitute into the implicit equation for the

curve (or surface) and solve for t.

Thus, if the implicit equation for the standard

ellipse is written:

(1/a)*(x-xc)**2+ (1/b)*(y-yc)**2=1

Then the center of the ellipse is at:

(xc,yc) and the semimajor or semiminor

axes are sqrt(a) and sqrt(b). If a and b have the same value, then

you have a circle.

Perform the substitution and rearrange the terms

into the form of the quadratic equation. If the

determinant is < 0, the roots are imaginary and

there is no intersection.

This approach may be extended to any quadratic curve

or surface.

- DL

[CS411X] How do I set the location of a component?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 2 Feb 1999 12:19:36 -0500

Hi All,

In the last CS510 class, I used the

resize method to set the location of a component.

I have just learned that this usage has been deprecated

*SURPRISE!*

To set the location of a component, without using the

layout manager, use:

setLocation(int x, int y);

Using this technique, you should be able to derive a

custom component layout that is editable using mouse

interaction.

- DL

[CS411X] How do I install Java3D?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 27 Oct 1998 19:19:57 -0400

To install Java3D on your windows systems...just

follow these 11 easy steps:

1) Download the following software:

a) Java 3D 1.1 Beta 1 API

b) Java Plug-in 1.1.1

c) Java Plug-in HTML Converter

d) JDK 1.2 Beta 4

f) JRE 1.2 Beta 4

2) Install JDK 1.2 Beta 4.

3) Install JRE 1.2 Beta 4 into JDK's JRE Directory.

4) Install Java 3D 1.1 Beta 1 API into the JRE Directory.

5) Install Java Plug-in 1.1.1 into the Plug-in directory of your

browser.

Enter the Advanced Settings and use your JRE 1.2 (\jdk\jre).

6) Install Java Plug-in HTML Converter.

Choose the "specific" option when asked.

7) Edit your environment variables to point to the 3D-classes and

3D-dll's, e.g.:

CLASSPATH

c:\jdk\jre\lib\ext\j3dutils.jar;c:\jdk\jre\lib\ext\j3dcore.jar;c:\jdk\jre\lib\ex

t\vecmath.jar;e:\jdk\jre\lib\ext\j3daudio.jar;e:\jdk\jre\lib\ext\iiimp.jar;.; P

ATH

c:\jdk\jre\bin;c:\jdk\bin;

8) Reboot.

9) Go ahead and compile HelloUniverse.java.

10) Use the HTML-Converter on that directory.

11) Open the HelloUniverse.html inside your browser.

Simple Yes?

- DL

[CS411X] How do I draw Points in 3D in Java?

Dr. Douglas Lyon ( lyon@snet.net)

Thu, 8 Oct 1998 12:02:46 -0500

Hi All,

Here is a nice little program for drawing the points around

a cynlinder...It zooms you in from infinity...

Give it a try!

- DL

import java.awt.*;

import java.awt.image.*;

public class DrawPoints extends

java.applet.Applet

implements Runnable {

Thread animationThread = null;

int xsize,ysize,xcenter,ycenter;

int delay=10;

int numberOfPoints=1000;

Graphics backGC;

Image backBuffer;

int[] starX,starY,starZ;

Color[] grayScale;

public static void main(String args[]) {

Frame f = new Frame();

DrawPoints s = new DrawPoints();

f.add(s);

f.setSize(256,256);

f.show();

s.init();

s.start();

}

public void init()

{

//Get screen dimensions

xsize=size().width;

ysize=size().height;

xcenter=xsize/2;

ycenter=ysize/2;

//Init double-buffering

backBuffer = createImage(xsize, ysize);

backGC = backBuffer.getGraphics();

starX=new int[numberOfPoints];

starY=new int[numberOfPoints];

starZ=new int[numberOfPoints];

double theta = 0;

double eps = (1.0/numberOfPoints) * 2*Math.PI;

for (int n=0;n<numberOfPoints;n++) {

starX[n]=(int)

((Math.sin(theta)*xsize*2.0)-xsize/2);

starY[n]=(int)

((Math.cos(theta)*ysize*2.0)-ysize/2);

starZ[n]=(int)

(Math.random()*4095);

theta = theta + eps;

}

//Create grayscale tones

grayScale=new Color[256];

for (int n=0;n<256;n++)

grayScale[255-n]=new Color(n,n,n);

}

//This method is called when the applet becomes visible

public void start()

{

//Create a thread and start it

if(animationThread == null)

{

animationThread = new Thread(this);

animationThread.start();

}

}

//This method is called when the applet becomes invisible

public void stop()

{

//Stop animation thread

animationThread = null;

}

public void run()

{

long time = System.currentTimeMillis();

while (animationThread != null)

{

//Make sure the frame rate is constant by using the

system clock

try

{

time += delay;

Thread.sleep(Math.max(

0, time - System.currentTimeMillis()));

}

catch (InterruptedException e){};

//Initiate a repaint of the screen

repaint();

}

}

public void paint(Graphics g)

{

//Clear screen

backGC.setColor(Color.black);

backGC.fillRect(0,0,xsize,ysize);

for (int n=0;n<numberOfPoints;n++)

{

//Move stars and clip against viewplane

//The back clipping plane and the

// view plane are hard coded

//for optimizing reasons.

// Viewplane=512, backplane=4095

starZ[n]-=50;

if (starZ[n]<512) starZ[n]=4095;

int z=starZ[n];

//Apply perspective projection

int x=(starX[n]<<9)/z+xcenter;

int y=(starY[n]<<9)/z+ycenter;

//Apply dept shading

backGC.setColor(grayScale[z>>4]);

//Draw star

backGC.drawLine(x,y,x,y);

}

//Draw buffer to screen

g.drawImage(backBuffer, 0, 0, this);

}

public void update(Graphics g) {

paint(g);

}

}

[CS411X] how do I build servelets in Java?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 29 Sep 1998 04:37:25 -0500

// This example is from _Java Examples in a Nutshell_. ( http://www.oreilly.com)

// Copyright (c) 1997 by David Flanagan

// This example is provided WITHOUT ANY WARRANTY either expressed or implied.

// You may study, use, modify, and distribute it for non-commercial purposes.

// For any commercial use, see http://www.davidflanagan.com/javaexamples

import java.io.*;

import java.net.*;

import java.util.*;

/**

* This class is a generic framework for a flexible, multi-threaded server.

* It listens on any number of specified ports, and, when it receives a

* connection on a port, passes input and output streams to a specified Service

* object which provides the actual service. It can limit the number of

* concurrent connections, and logs activity to a specified stream.

**/

public class Server {

/**

* A main() method for running the server as a standalone program.

* The command-line arguments to the program should be pairs of servicenames

* and port numbers. For each pair, the program will dynamically load the

* named Service class, instantiate it, and tell the server to provide that

* Service on the specified port. The special -control argument should be

* followed by a password and port, and will start special server control

* service running on the specified port, protected by the specified

* password.

**/

public static void main(String[] args) {

try {

if (args.length < 2) // Check number of arguments

throw new IllegalArgumentException("Must start at least one service");

// Create a Server object that uses standard out as its log and

// has a limit of ten concurrent connections at once.

Server s = new Server(System.out, 10);

// Parse the argument list

int i = 0;

while(i < args.length) {

if (args[i].equals("-control")) { // Handle the -control argument

i++;

String password = args[i++];

int port = Integer.parseInt(args[i++]);

s.addService(new Control(s, password), port); // add control service

}

else {

// Otherwise start a named service on the specified port.

// Dynamically load and instantiate a class that implements Service.

String serviceName = args[i++];

Class serviceClass = Class.forName(serviceName); // dynamic load

Service service = (Service)serviceClass.newInstance(); // instantiate

int port = Integer.parseInt(args[i++]);

s.addService(service, port);

}

}

}

catch (Exception e) { // Display a message if anything goes wrong

System.err.println("Server: " + e);

System.err.println("Usage: java Server [-control <password> <port>] " +

"[<servicename> <port> ... ]");

System.exit(1);

}

}

// This is the state for the server

ConnectionManager connectionManager; // The ConnectionManager object

Hashtable services; // The current services and their ports

ThreadGroup threadGroup; // The threadgroup for all our threads

PrintWriter logStream; // Where we send our logging output to

/**

* This is the Server() constructor. It must be passed a stream

* to send log output to (may be null), and the limit on the number of

* concurrent connections. It creates and starts a ConnectionManager

* thread which enforces this limit on connections.

**/

public Server(OutputStream logStream, int maxConnections) {

setLogStream(logStream);

log("Starting server");

threadGroup = new ThreadGroup("Server");

connectionManager = new ConnectionManager(threadGroup, maxConnections);

connectionManager.start();

services = new Hashtable();

}

/**

* A public method to set the current logging stream. Pass null

* to turn logging off

**/

public void setLogStream(OutputStream out) {

if (out != null) logStream = new PrintWriter(new OutputStreamWriter(out));

else logStream = null;

}

/** Write the specified string to the log */

protected synchronized void log(String s) {

if (logStream != null) {

logStream.println("[" + new Date() + "] " + s);

logStream.flush();

}

}

/** Write the specified object to the log */

protected void log(Object o) { log(o.toString()); }

/**

* This method makes the server start providing a new service.

* It runs the specified Service object on the specified port.

**/

public void addService(Service service, int port) throws IOException {

Integer key = new Integer(port); // the hashtable key

// Check whether a service is already on that port

if (services.get(key) != null)

throw new IllegalArgumentException("Port " + port + " already in use.");

// Create a Listener object to listen for connections on the port

Listener listener = new Listener(threadGroup, port, service);

// Store it in the hashtable

services.put(key, listener);

// Log it

log("Starting service " + service.getClass().getName() +

" on port " + port);

// Start the listener running.

listener.start();

}

/**

* This method makes the server stop providing a service on a port.

* It does not terminate any pending connections to that service, merely

* causes the server to stop accepting new connections

**/

public void removeService(int port) {

Integer key = new Integer(port); // hashtable key

// Look up the Listener object for the port in the hashtable of services

final Listener listener = (Listener) services.get(key);

if (listener == null) return;

// Ask the listener to stop

listener.pleaseStop();

// Remove it from the hashtable

services.remove(key);

// And log it.

log("Stopping service " + listener.service.getClass().getName() +

" on port " + port);

}

/**

* This nested Thread subclass is a "listener". It listens for connections

* on a specified port (using a ServerSocket) and when it gets a connection

* request, it calls a method of the ConnectionManager to accept (or reject)

* the connection. There is one Listener for each Service being provided

* by the Server. The Listener passes the Server object to the

* ConnectionManager, but doesn't do anything with it itself.

*/

public class Listener extends Thread {

ServerSocket listen_socket; // The socket we listen for connections on

int port; // The port we're listening on

Service service; // The service to provide on that port

boolean stop = false; // Whether we've been asked to stop

/**

* The Listener constructor creates a thread for itself in the specified

* threadgroup. It creates a ServerSocket to listen for connections

* on the specified port. It arranges for the ServerSocket to be

* interruptible, so that services can be removed from the server.

**/

public Listener(ThreadGroup group, int port, Service service)

throws IOException {

super(group, "Listener:" + port);

listen_socket = new ServerSocket(port);

// give the socket a non-zero timeout so accept() can be interrupted

listen_socket.setSoTimeout(600000);

this.port = port;

this.service = service;

}

/** This is the nice way to get a Listener to stop accepting connections */

public void pleaseStop() {

this.stop = true; // set the stop flag

this.interrupt(); // and make the accept() call stop blocking

}

/**

* A Listener is a Thread, and this is its body.

* Wait for connection requests, accept them, and pass the socket on

* to the ConnectionManager object of this server

**/

public void run() {

while(!stop) { // loop until we're asked to stop.

try {

Socket client = listen_socket.accept();

connectionManager.addConnection(client, service);

}

catch (InterruptedIOException e) {}

catch (IOException e) {log(e);}

}

}

}

/**

* This nested class manages client connections for the server.

* It maintains a list of current connections and enforces the

* maximum connection limit. It creates a separate thread (one per

* server) that sits around and wait()s to be notify()'d that a connection

* has terminated. When this happens, it updates the list of connections.

**/

public class ConnectionManager extends Thread {

int maxConnections; // The maximum number of allowed connections

Vector connections; // The current list of connections

/**

* Create a ConnectionManager in the specified thread group to enforce

* the specified maximum connection limit. Make it a daemon thread so

* the interpreter won't wait around for it to exit.

**/

public ConnectionManager(ThreadGroup group, int maxConnections) {

super(group, "ConnectionManager");

this.setDaemon(true);

this.maxConnections = maxConnections;

connections = new Vector(maxConnections);

log("Starting connection manager. Max connections: " + maxConnections);

}

/**

* This is the method that Listener objects call when they accept a

* connection from a client. It either creates a Connection object

* for the connection and adds it to the list of current connections,

* or, if the limit on connections has been reached, it closes the

* connection.

**/

synchronized void addConnection(Socket s, Service service) {

// If the connection limit has been reached

if (connections.size() >= maxConnections) {

try {

PrintWriter out = new PrintWriter(s.getOutputStream());

// Then tell the client it is being rejected.

out.println("Connection refused; " +

"server has reached maximum number of clients.");

out.flush();

// And close the connection to the rejected client.

s.close();

// And log it, of course

log("Connection refused to " + s.getInetAddress().getHostAddress() +

":" + s.getPort() + ": max connections reached.");

} catch (IOException e) {log(e);}

}

else { // Otherwise, if the limit has not been reached

// Create a Connection thread to handle this connection

Connection c = new Connection(s, service);

// Add it to the list of current connections

connections.addElement(c);

// Log this new connection

log("Connected to " + s.getInetAddress().getHostAddress() +

":" + s.getPort() + " on port " + s.getLocalPort() +

" for service " + service.getClass().getName());

// And start the Connection thread running to provide the service

c.start();

}

}

/**

* A Connection object calls this method just before it exits.

* This method uses notify() to tell the ConnectionManager thread

* to wake up and delete the thread that has exited.

**/

public synchronized void endConnection() { this.notify(); }

/** Change the current connection limit */

public synchronized void setMaxConnections(int max) { maxConnections=max; }

/**

* Output the current list of connections to the specified stream.

* This method is used by the Control service defined below.

**/

public synchronized void printConnections(PrintWriter out) {

for(int i = 0; i < connections.size(); i++) {

Connection c = (Connection)connections.elementAt(i);

out.println("CONNECTED TO " +

c.client.getInetAddress().getHostAddress() + ":" +

c.client.getPort() + " ON PORT " + c.client.getLocalPort()+

" FOR SERVICE " + c.service.getClass().getName());

}

}

/**

* The ConnectionManager is a thread, and this is the body of that

* thread. While the ConnectionManager methods above are called by other

* threads, this method is run in its own thread. The job of this thread

* is to keep the list of connections up to date by removing connections

* that are no longer alive. It uses wait() to block until notify()'d by

* the endConnection() method.

**/

public void run() {

while(true) { // infinite loop

// Check through the list of connections, removing dead ones

for(int i = 0; i < connections.size(); i++) {

Connection c = (Connection)connections.elementAt(i);

if (!c.isAlive()) {

connections.removeElementAt(i);

log("Connection to " + c.client.getInetAddress().getHostAddress() +

":" + c.client.getPort() + " closed.");

}

}

// Now wait to be notify()'d that a connection has exited

// When we wake up we'll check the list of connections again.

try { synchronized(this) { this.wait(); } }

catch(InterruptedException e) {}

}

}

}

/**

* This class is a subclass of Thread that handles an individual connection

* between a client and a Service provided by this server. Because each

* such connection has a thread of its own, each Service can have multiple

* connections pending at once. Despite all the other threads in use, this

* is the key feature that makes this a multi-threaded server implementation.

**/

public class Connection extends Thread {

Socket client; // The socket to talk to the client through

Service service; // The service being provided to that client

/**

* This constructor just saves some state and calls the superclass

* constructor to create a thread to handle the connection. Connection

* objects are created by Listener threads. These threads are part of

* the server's ThreadGroup, so all Connection threads are part of that

* group, too.

**/

public Connection(Socket client, Service service) {

super("Server.Connection:" + client.getInetAddress().getHostAddress() +

":" + client.getPort());

this.client = client;

this.service = service;

}

/**

* This is the body of each and every Connection thread.

* All it does is pass the client input and output streams to the

* serve() method of the specified Service object. That method

* is responsible for reading from and writing to those streams to

* provide the actual service. Recall that the Service object has been

* passed from the Server.addService() method to a Listener object

* to the ConnectionManager.addConnection() to this Connection object,

* and is now finally getting used to provide the service.

* Note that just before this thread exits it calls the

* ConnectionManager.endConnection() method to wake up the

* ConnectionManager thread so that it can remove this Connection

* from its list of active connections.

**/

public void run() {

try {

InputStream in = client.getInputStream();

OutputStream out = client.getOutputStream();

service.serve(in, out);

}

catch (IOException e) {log(e);}

finally { connectionManager.endConnection(); }

}

}

/**

* Here is the Service interface that we have seen so much of.

* It defines only a single method which is invoked to provide the service.

* serve() will be passed an input stream and an output stream to the client.

* It should do whatever it wants with them, and should close them before

* returning.

*

* All connections through the same port to this service share a single

* Service object. Thus, any state local to an individual connection must

* be stored in local variables within the serve() method. State that should

* be global to all connections on the same port should be stored in

* instance variables of the Service class. If the same Service is running

* on more than one port, there will typically be different Service instances

* for each port. Data that should be global to all connections on any port

* should be stored in static variables.

*

* Note that implementations of this interface must have a no-argument

* constructor if they are to be dynamically instantiated by the main()

* method of the Server class.

**/

public interface Service {

public void serve(InputStream in, OutputStream out) throws IOException;

}

/**

* A very simple service. It displays the current time on the server

* to the client, and closes the connection.

**/

public static class Time implements Service {

public void serve(InputStream i, OutputStream o) throws IOException {

PrintWriter out = new PrintWriter(new OutputStreamWriter(o));

out.println(new Date());

out.close();

i.close();

}

}

/**

* This is another example service. It reads lines of input from the

* client, and sends them back, reversed. It also displays a welcome

* message and instructions, and closes the connection when the user

* enters a '.' on a line by itself.

**/

public static class Reverse implements Service {

public void serve(InputStream i, OutputStream o) throws IOException {

BufferedReader in = new BufferedReader(new InputStreamReader(i));

PrintWriter out =

new PrintWriter(new BufferedWriter(new OutputStreamWriter(o)));

out.println("Welcome to the line reversal server.");

out.println("Enter lines. End with a '.' on a line by itself");

for(;;) {

out.print("> ");

out.flush();

String line = in.readLine();

if ((line == null) || line.equals(".")) break;

for(int j = line.length()-1; j >= 0; j--)

out.print(line.charAt(j));

out.println();

}

out.close();

in.close();

}

}

/**

* This service is an HTTP mirror, just like the HttpMirror class

* implemented earlier in this chapter. It echos back the client's

* HTTP request

**/

public static class HTTPMirror implements Service {

public void serve(InputStream i, OutputStream o) throws IOException {

BufferedReader in = new BufferedReader(new InputStreamReader(i));

PrintWriter out = new PrintWriter(new OutputStreamWriter(o));

out.println("HTTP/1.0 200 ");

out.println("Content-Type: text/plain");

out.println();

String line;

while((line = in.readLine()) != null) {

if (line.length() == 0) break;

out.println(line);

}

out.close();

in.close();

}

}

/**

* This service demonstrates how to maintain state across connections

* by saving it in instance variables and using synchronized access to

* those variables. It maintains a count of how many clients have connected

* and tells each client what number it is

**/

public static class UniqueID implements Service {

public int id=0;

public synchronized int nextId() { return id++; }

public void serve(InputStream i, OutputStream o) throws IOException {

PrintWriter out = new PrintWriter(new OutputStreamWriter(o));

out.println("You are client #: " + nextId());

out.close();

i.close();

}

}

/**

* This is a non-trivial service. It implements a command-based protocol

* that gives password-protected runtime control over the operation of the

* server. See the main() method of the Server class to see how this

* service is started.

*

* The recognized commands are:

* password: give password; authorization is required for most commands

* add: dynamically add a named service on a specified port

* remove: dynamically remove the service running on a specified port

* max: change the current maximum connection limit.

* status: display current services, connections, and connection limit

* help: display a help message

* quit: disconnect

*

* This service displays a prompt, and sends all of its output to the user

* in capital letters. Only one client is allowed to connect to this service

* at a time.

**/

public static class Control implements Service {

Server server; // The server we control

String password; // The password we require

boolean connected = false; // Whether a client is already connected to us

/**

* Create a new Control service. It will control the specified Server

* object, and will require the specified password for authorization

* Note that this Service does not have a no argument constructor, which

* means that it cannot be dynamically instantiated and added as the other,

* generic services above can be.

**/

public Control(Server server, String password) {

this.server = server;

this.password = password;

}

/**

* This is the serve method that provides the service. It reads a line

* the client, and uses java.util.StringTokenizer to parse it into

* commands and arguments. It does various things depending on the

* command.

**/

public void serve(InputStream i, OutputStream o) throws IOException {

// Setup the streams

BufferedReader in = new BufferedReader(new InputStreamReader(i));

PrintWriter out = new PrintWriter(new OutputStreamWriter(o));

String line;

boolean authorized = false; // Has the user has given the password yet?

int num;

// If there is already a client connected to this service, display a

// message to this client and close the connection. We use a

// synchronized block to prevent a race condition.

synchronized(this) {

if (connected) {

out.println("ONLY ONE CONTROL CONNECTION ALLOWED AT A TIME.");

out.close();

return;

}

else connected = true;

}

for(;;) { // infinite loop

out.print("> "); // Display a prompt

out.flush(); // Make it appear right away

line = in.readLine(); // Get the user's input

if (line == null) break; // Quit if we get EOF.

try {

// Use a StringTokenizer to parse the user's command

StringTokenizer t = new StringTokenizer(line);

if (!t.hasMoreTokens()) continue; // if input was blank line

// Get the first word of the input and convert to lower case

String command = t.nextToken().toLowerCase();

// Now compare it to each of the possible commands, doing the

// appropriate thing for each command

if (command.equals("password")) { // Password command

String p = t.nextToken(); // Get the next word of input

if (p.equals(this.password)) { // Does it equal the password

out.println("OK"); // Say so

authorized = true; // Grant authorization

}

else out.println("INVALID PASSWORD"); // Otherwise fail

}

else if (command.equals("add")) { // Add Service command

// Check whether password has been given

if (!authorized) out.println("PASSWORD REQUIRED");

else {

// Get the name of the service and try to dynamically load

// and instantiate it. Exceptions will be handled below

String serviceName = t.nextToken();

Class serviceClass = Class.forName(serviceName);

Service service;

try { service = (Service) serviceClass.newInstance(); }

catch (NoSuchMethodError e) {

throw new IllegalArgumentException("Service must have a " +

"no-argument constructor");

}

int port = Integer.parseInt(t.nextToken());

// If no exceptions occurred, add the service

server.addService(service, port);

out.println("SERVICE ADDED"); // acknowledge

}

}

else if (command.equals("remove")) { // Remove service command

if (!authorized) out.println("PASSWORD REQUIRED");

else {

int port = Integer.parseInt(t.nextToken()); // get port

server.removeService(port); // remove the service on it

out.println("SERVICE REMOVED"); // acknowledge

}

}

else if (command.equals("max")) { // Set max connection limit

if (!authorized) out.println("PASSWORD REQUIRED");

else {

int max = Integer.parseInt(t.nextToken()); // get limit

server.connectionManager.setMaxConnections(max); // set limit

out.println("MAX CONNECTIONS CHANGED"); // acknowledge

}

}

else if (command.equals("status")) { // Status Display command

if (!authorized) out.println("PASSWORD REQUIRED");

else {

// Display a list of all services currently running

Enumeration keys = server.services.keys();

while(keys.hasMoreElements()) {

Integer port = (Integer) keys.nextElement();

Listener listener = (Listener)server.services.get(port);

out.println("SERVICE " + listener.service.getClass().getName()+

" ON PORT " + port);

}

// Display a list of all current connections

server.connectionManager.printConnections(out);

// Display the current connection limit

out.println("MAX CONNECTIONS: " +

server.connectionManager.maxConnections);

}

}

else if (command.equals("help")) { // Help command

// Display command syntax. Password not required

out.println("COMMANDS:\n" +

"\tpassword <password>\n" +

"\tadd <service> <port>\n" +

"\tremove <port>\n" +

"\tmax <max-connections>\n" +

"\tstatus\n" +

"\thelp\n" +

"\tquit");

}

else if (command.equals("quit")) break; // Quit command. Exit.

else out.println("UNRECOGNIZED COMMAND"); // Unknown command error

}

catch (Exception e) {

// If an exception occurred during the command, print an error

// message, then output details of the exception.

out.println("EXCEPTION WHILE PARSING OR EXECUTING COMMAND:");

out.println(e);

}

}

// Finally, when the loop command loop ends, close the streams

// and set our connected flag to false so that other clients can

// now connect.

out.close();

in.close();

connected = false;

}

}

}

[CS411X] How do I grab a frame?

Dr. Douglas Lyon ( lyon@snet.net)

Sun, 27 Sep 1998 07:08:38 -0500

// Copyright 1998, Prof. D. Lyon

//

import java.awt.*;

import quicktime.qd.*;

import quicktime.*;

import quicktime.std.StdQTConstants;

import quicktime.std.sg.*;

import quicktime.app.image.*;

import java.io.*;

public class FrameGrab

implements

StdQTConstants {

public static void main (String args[]) {

FrameGrab fg = new FrameGrab();

fg.snapShot();

System.out.println("click");

}

private SequenceGrabber sg;

public static Image pictToImage(Pict inPict) {

ImageData id = null;

try {

id.fromPict(inPict);

} catch (Exception e) {

System.out.println(e);

};

QDRect r = id.getDisplayBounds();

Image i = null;

try {

i =

Toolkit.getDefaultToolkit().createImage(new

QTImageProducer(

id, new

Dimension(

r.getWidth(), r.getHeight())));

}

catch (Exception e) {

System.out.println(e);

}

return i;

}

public void toFile() {

FileDialog fd = new FileDialog(

new Frame(),

"Gimme a pict name",

FileDialog.SAVE);

fd.show();

String fn= fd.getDirectory()+fd.getFile();

toFile(fn);

}

public void toFile(String fn) {

File file =

new File(fn);

Pict p = getPict();

try {

p.writeToFile(file);

}

catch (Exception e) {

System.out.println(e);

};

}

public Image getImage() {

return pictToImage(getPict());

}

public Pict getPict() {

try {

sg = new SequenceGrabber();

}

catch (Exception e) {

System.out.println(e);

};

int offScreenDepth=8;

int grabPictFlags =

seqGrabToMemory |

seqGrabPreview |

seqGrabRecord |

seqGrabPlayDuringRecord ;

QDRect bounds=new QDRect(256,256);

Pict p = null;

try {

p = Pict.fromSequenceGrabber(

sg,

bounds,

offScreenDepth,

grabPictFlags);

}

catch (Exception e) {};

return p;

}

private void snapShot() {

try{

QTSession.open();

toFile();

} catch (Exception ee) {

ee.printStackTrace();

QTSession.close();

}

}

}

[CS411X] How do I play notes in Java?

Dr. Douglas Lyon ( lyon@snet.net)

Sat, 26 Sep 1998 06:31:51 -0500

>>QTSession.open();

>>NoteAllocator myAllo = new NoteAllocator();

>>NoteChannel myChan = new NoteChannel(myAllo, 25);

>>myChan.playNote(62, 127);

>>

>>all this is great.. but it drops out to time [badly] when i loop it:

>>

>>QTSession.open();

>>NoteAllocator myAllo = new NoteAllocator();

>>NoteChannel myChan = new NoteChannel(myAllo, 25);

>>

>>while(true){

>> myChan.playNote (61, 127);

>> delay(na, 1500);

>> myChan.playNote (61, 0);

>>}

>>

>>static void delay (NoteAllocator na, long ms) {

>> try { myAllo.task(); Thread.sleep(ms); }

>> catch (Exception e) { e.printStackTrace(); }

>>}

>

>The problem here is probably in the latency of threads that seem to plague

>Java implementations. You can try the Object.wait methods - I've recently

>been talking about this with Patrick and he thought that they may get a

>more accurate timing response.

>

>>this seems to go out of time (is there a better way????)... if not i've had

>>a rethink..

>>

>>what if i set up an bite array [or of the like] that has a list of note

>>numbers that would b played one at time (ie timeStamped) [62, 63, 64, 65,

>>66].. then pass this list to my channel to play and loop.. (as if it was

>>playing a file..)

>>

>>.. but the thing i also need to do is change one of the notes in the list

>>(at a random time) say 65 to 42 that would give us a list of [62, 63, 64,

>>42, 66].

>

>The QTMusic architecture does exactly this kind of thing and you will get a

>lot better timing from QT itself than from Java. You could use the

>TunePlayer itself or create a movie adding music data to the movie and then

>just playing the movie. There is a pdf document on the qt web site

>(http://www.apple.com/quicktime/developers/) that is completely devoted to

>the music architecture.

[CS411X] How will I earn a grade in Embedded Control?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 25 Sep 1998 08:08:05 -0500

For those who are

earning a grade in embedded control;

You must write up the labs

as we complete them. This will be the basis for

your grade in the course. As a result, there

will be no final or midterm.

Labs are graded for there English content.

Labs must be submitted on paper, but should be

in an electronic format so that they can also

appear on the web. Web conversion will

occur only after the labs have been graded and

approved.

I can assist you with the web conversion, if you submit

the lab on floppy.

The lab should be written to give the student

enough information to perform the task.

That is:

Like a cook book!

For example:

Pancakes - yields 15 pancakes + PhD

Materials:

1.5 cps flour, 2.5 tsp baking pdr, 2 cps milk

Procedure:

Use medium to hot heat. Use non-stick spray. Raise

temperature to leyden frost point (drops dance on pan).

mix well, place in heated, greased pan, 1/8 cp at a time.

Objective:

Describe basic physics behind leyden frost point.

Compute the vapor pressure of mixture.

Measure the temperature of pan.

Devise a robtic control mechanism for automating

the pancake production process. Describe the

sensor feedback systems needed to detect

doneness and flip pancakes.

Limit your self to a robot with two arms.

Vision is permitted as a sensor.

Topics for further research:

How does cold batter cool the surface of

the hot pan?

Are pan-cakes better if flipped before they are

cooked all the way on one side?

Which of the Navier-Stokes terms may be reduced

from the mix-flow equations, using destructive modeling?

Are batters thixotropic?

Can level set methods be used to compute the pancake

boundary's growth?

------------------------

I have written up the below experiment in a first

draft form. For credit, you must complete

and flesh out the lab. Plan on writing a total

of about 3-5 pages.

Experiment 1: The Serial Port

Objectives

After performing this experiment, you will be able to

Explain the operation of the serial port

Contruct a driver for interface to the serial port

Draw a timing diagram of the data stream to and from the

serial port.

Explain the use of the framing and parity bits.

Materials Needed

Serial Cable

Computer, with Java

Modem

Summary of Theory

The serial port simplifies the interconnection of

computers and peripherals by providing a simple

three wire interface. It also has a more elaborate

interface which uses hardware handshaking.

The serial interface support bi-directional data

transmission.

(explain duplex, full and half, as well as the

the control lines).

Procedure

1. For this experiment, a modem is hooked to a computer.

Use a terminal program to verify that the modem is connected

correctly. The command:

atdt5551234

Should cause the modem to dial, with an audible ring.

2. use the following Java program to drive the serial

port and make the modem dial out.

3. Using the following AT modem command set, vary

the delay between the touch tones.

4. Alter the program to make the delay between the touch

tones a parameter which is passed to dialing string.

Report for experiment 1

Name:_________________ Date:________________

Objectives

Explain the operation of the rs-232 port.

Construct a serial port driver and interface your

computer with a modem.

Draw a timing diagram for the handshake and data:

DSR

DTR

TX

RX

Results and Conclusions:

Topics for further investigation:

Evaluation and Review Questions

1. Why doesn't the serial port transmitter overload the

serial port reciever?

2. How does the serial port detect the handshake signals

that come back from the controller?

3. Is negative or positive-true logic used for the handshaking?

[CS411X] How do I capture a video sequence?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 25 Sep 1998 08:08:05 -0500

/*

* quicktime.app: Sample Code for Initial Seeding

*

* © 1996, 97 Copyright, Apple Computer

* All rights reserved

*/

// This gives you a good summary of the

// classes that are used in this demo

import java.awt.*;

import java.awt.event.*;

import quicktime.qd.*;

import quicktime.*;

import quicktime.util.QTUtils;

import quicktime.app.util.*;

import quicktime.io.*;

import quicktime.std.StdQTConstants;

import quicktime.std.sg.*;

import quicktime.app.sg.SGDrawer;

import quicktime.app.util.*;

import quicktime.std.movies.*;

import quicktime.app.display.QTCanvas;

public class SGCapture extends Frame implements WindowListener,

StdQTConstants, Errors {

static final int kWidth = 320;

static final int kHeight = 240;

public static void main (String args[]) {

try {

SGCapture pm = new SGCapture("QT in Java");

pm.show();

pm.toFront();

} catch (Exception e) {

e.printStackTrace();

QTSession.close();

}

}

void createMovie () throws QTException {

FileDialog fd = new FileDialog (this, "Save Movie As...",

FileDialog.SAVE);

fd.show();

if(fd.getFile() == null)

throw new QTIOException (userCanceledErr, "");

mFile = new QTFile(fd.getDirectory() + fd.getFile());

mMovie = Movie.createMovieFile (mFile,

kMoviePlayer,

createMovieFileDeleteCurFile |

createMovieFileDontCreateResFile);

}

SGCapture (String title) {

super (title);

try {

QTSession.open();

myQTCanvas = new

QTCanvas(QTCanvas.kPerformanceResize, 0.5F, 0.5F);

myQTCanvas.setMaximumSize (new Dimension (640, 480));

setLayout (new BorderLayout());

add ("Center", myQTCanvas);

addNotify();

Insets insets = insets();

setBounds (0, 0, (insets.left + insets.right +

kWidth), (insets.top + insets.bottom + kHeight));

addWindowListener(this);

} catch (Exception ee) {

ee.printStackTrace();

QTSession.close();

}

}

private QTCanvas myQTCanvas;

private SGSoundChannel mAudio;

private SGDrawer mDrawable;

private QTFile mFile;

private Movie mMovie;

public void windowClosing (WindowEvent e) {

myQTCanvas.removeClient();

QTSession.close();

dispose();

}

public void windowIconified (WindowEvent e) {

}

public void windowDeiconified (WindowEvent e) {

}

public void windowClosed (WindowEvent e) {

System.exit(0);

}

public void windowOpened (WindowEvent e) {

try{

createMovie();

SequenceGrabber mGrabber = new SequenceGrabber();

SGVideoChannel mVideo = new SGVideoChannel(mGrabber);

mVideo.settingsDialog ();

mVideo.setBounds (new QDRect(kWidth, kHeight));

mVideo.setUsage (seqGrabPreview | seqGrabRecord |

seqGrabPlayDuringRecord); // seqGrabRecord

mAudio = new SGSoundChannel(mGrabber);

mAudio.setUsage (seqGrabPreview | seqGrabRecord |

seqGrabPlayDuringRecord); // seqGrabRecord

mAudio.setVolume (2);

mDrawable = new SGDrawer(mVideo);

myQTCanvas.setClient(mDrawable,true);

mGrabber.setDataOutput (mFile, seqGrabPreview |

seqGrabRecord | seqGrabPlayDuringRecord);

mGrabber.prepare(true,true);

mGrabber.startPreview();

} catch (Exception ee) {

ee.printStackTrace();

QTSession.close();

}

}

public void windowActivated (WindowEvent e) {}

public void windowDeactivated (WindowEvent e) {}

}

[CS411X] How do I set the flags to grab a frame?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 25 Sep 1998 08:08:05 -0500

That seems to

depend on the application.

int flags =

seqGrabPreview |

seqGrabRecord |

seqGrabPlayDuringRecord;

[CS411X] How do I convert from pict to image?

Dr. Douglas Lyon ( lyon@snet.net)

Thu, 24 Sep 1998 05:35:22 -0500

Hi All,

Once you have an instance of a Pict class,

is there a conversion process that will

yield an instance of a Java Image class?

Image pictToImage(Pict inPict) {

ImageData data = ImageData.fromPict(inPict);

QDRect r = data.getDisplayBounds();

return Toolkit.getDefaultToolkit().createImage(new

QTImageProducer(data, new Dimension(r.getWidth(), r.getHeight())));

}

[CS411X] How do I get a printed copy of QT-Components?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 22 Sep 1998 06:18:54 -0500

http://developer.apple.com/techpubs/mac/QTComponents/QTComponents-2.html

Has the PDF link...

- DL

[CS411X] how do I get QT4Java?

Dr. Douglas Lyon ( lyon@snet.net)

Tue, 22 Sep 1998 06:16:25 -0500

There is a new build available on the server:

http://qtj.apple.com/biscotti

username: kaleida

password: newton

[CS411X] How do I learn about digitizing video?

Dr. Douglas Lyon ( lyon@snet.net)

Mon, 21 Sep 1998 11:01:35 -0500

http://developer.apple.com/techpubs/mac/QTComponents/QTComponents-377.html#HEADI

NG377-0

The above url will take you to the QT Components

documentation on digitizing video. This will work on

any platform that support quicktime.

- DL

[CS411X] How do I install the COMM API on NT?

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 18 Sep 1998 07:46:01 -0500

copy

win32com.ddl

into the

c:\winnt\system

Drag the jar file to the CW project window.

- DL

[CS411X] How do I drive a serial line-based controller? Part2

Dr. Douglas Lyon ( lyon@snet.net)

Fri, 18 Sep 1998 07:44:28 -0500

In my last e-mail on this

subject...I realized that:

String s = "M,0,0,0,0,0,0,7,0,0";

could be:

String s = "M,0,0,0,0,0,0,7,0,0\r\f";

byte b[] = s.getBytes();

Should be enough!

Check the value of the last two bytes by writing

them as int values to the console...is it 13 and 10?

- DL

>To formulate a string+ control

>characters to an embedded controller, you need to formulate

>to different byte arrays and concatenate them.

>

> byte [] st={'M',0,0,0,0,0,0,7,0,0,13,10}; // have

>

>Should be:

>

>String s = "M,0,0,0,0,0,0,7,0,0";

>byte b[] = s.getBytes();

>byte eb[] = {13,10};

>byte turnBytes[] = new byte[b.length+eb.length];

>int i=0;

>for (; i < b.length; i++) {

> turnBytes [i]=b[i];

>}

>turnBytes[i]=eb[0];

>turnBytes[i+1]=eb[1];

>

>now write out the turnBytes....

>

>Got it?

>

> - DL

>

>

>>Hi!

>>

>>Here is my code.

>>If you can solve the problem, send me a email.

>>

>>-Hak Kywn Roh

>>

>>// Hak Kywn Roh (0367641)

>>// CPE388X

>>// Assignment #1

>>

>>import java.io.*;

>>import java.util.*;

>>import javax.comm.*;

>>

>>public class TurnTable

>>{

>> static Enumeration portList;

>> static CommPortIdentifier portId;

>> static SerialPort serialPort;

>> static OutputStream outputStream;

>>

>> public static void main(String[] args)

>> {

>> TurnTable tt=new TurnTable();

>> System.out.println("getPortIdentifiers...");

>> portList=CommPortIdentifier.getPortIdentifiers();

>> System.out.println("getPortIdentifiers... done!");

>>

>> while (portList.hasMoreElements())

>> {

>> portId=(CommPortIdentifier)portList.nextElement();

>> if

>>(portId.getPortType()==CommPortIdentifier.PORT_SERIAL)

>> {

>>

>> if (portId.getName().equals("COM3"))

>> {

>>

>> System.out.println("portId="+portId.getName());

>> try

>> {

>>

>> serialPort=(SerialPort)portId.open("SimpleWriteApp", 2000);

>> System.out.println("Port

>>Open");

>> }

>> catch (PortInUseException e)

>> {

>>

>> System.out.println(e.currentOwner+" owned this port");

>> System.out.println("Will

>>try to close");

>> serialPort.close();

>> }

>> try

>> {

>>

>> outputStream=serialPort.getOutputStream();

>> }

>> catch (IOException e)

>> {

>> System.out.println("Could

>>not get output Stream:"+e);

>> }

>> try

>> {

>>

>> serialPort.setSerialPortParams(9600,SerialPort.DATABITS_8,

>>SerialPort.STOPBITS_2, SerialPort.PARITY_NONE);

>> }

>> catch

>>(UnsupportedCommOperationException e)

>> {

>> System.out.println("Set

>>Serial Port Params :"+e);

>> }

>> try

>> {

>> byte [] mn={27, 13, 27, 13, 27, 13, 0};

>> outputStream.write(mn);

>> System.out.println("Send

>>magic number..");

>> }

>> catch (IOException e)

>> {

>> System.out.println(e);

>> }

>>

>> sleepSec(10);

>>

>> try

>> {

>> byte [] st={'M',0,0,0,0,0,0,7,0,0,13,10}; // have

>>to change this line...

>> outputStream.write(st);

>> System.out.println("Move

>>step.");

>> }

>> catch (IOException e)

>> {

>> System.out.println(e);

>> }

>>

>> //tt.step(1);

>> //sleepSec(2);

>> //tt.step(2);

>> //sleepSec(2);

>> //tt.step(3);

>> //sleepSec(2);

>>

>> serialPort.close();

>> System.out.println("port closed");

>>

>> try {

>> System.in.read();

>> } catch (java.io.IOException e) {}

>> }

>> }

>> }

>> }

>>

>> public void step(int n)

>> {

>> System.out.println("Move "+n+" steps");

>> byte [] st={'M',0,0,0,0,0,0,7,0,0,13,10};

>> for (int i=0;i<n;i++)

>> try

>> {

>> outputStream.write(st);

>> }

>> catch (IOException e)

>> {

>> System.out.println(e);

>> }

>> }

>>

>> public static void sleepSec(int sec)

>> {

>> try

>> {

>> Thread.sleep(sec*1000);

>> }

>> catch (InterruptedException e) {}

>> }

>>}

[CS411X] How do I run quick-time for Java, under windows?

Dr. Douglas Lyon ( lyon@snet.net)

Wed, 16 Sep 1998 07:50:24 -0500

When running quick time for java under windows,

use:

c:\jdk1.2beta4\lib\tools.jar;c:\jdk1.2beta4\qt\lib\qtjava.zip;c:\oldjava

\java\lib\classes.zip

have the QTJavaNative.DLL file in the same directory as

> the QTJava.zip file. Also check that you have a classes.zip archive in the

> your JDK \lib directory. JDK 1.2b4 no longer includes classes.zip (they

> have broken it into several jar files)

[CS411X] how do I time image processing?

Dr. Douglas Lyon ( lyon@snet.net)

Thu, 7 May 1998 09:40:44 -0400

To time image processing tasks,

we can use the timer class.

To time the draw task, is a rather different

issue. One way is to create a memory image,

then get the graphics context from the image,

finally, draw to the image. When all the

drawing is done, display the image.

This requires that a new image be made each

time. This is really a waste!

What is needed is a way to clear the graphics

context before new invocations of paint.

....paint(Graphics g) {

g = g.create(0,0,g.getSize().width, g.getSize().height);

// now time the paint method...you have erased the old graphics context...

// does this work? I have not tried it.

// This is a waste too, because a new graphics context is

// created each time......Perhaps we should time

// this. - DL

}

>----------

>X-Sun-Data-Type: text

>X-Sun-Data-Description: text

>X-Sun-Data-Name: text

>X-Sun-Charset: us-ascii

>X-Sun-Content-Lines: 24

>

>

>Dear Professor Lyon:

>

>Here is a small test program that tests Timer.java class.

>I modified the Timer class before, cause I thought the

>problem is in the class. Even if I implement the test

>class for the "old" Timer.class that you sent, I think

>the results would be the same.

>

>You were absolutely right, that it is awt deep problem.

>That concludes the important observation that we cannot

>use System.currentTimeMillis() when we do image processing.

>What would be the good solution ?

>

>Thank you very much.

>

>

>

>Sincerely yours,

>

>

>Kirill Golubev

>

>

>----------

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>

>

>

>public class Timer {

>

> // private long startTime=0;

> // private long endTime=0;

>

> public long start() {

> long startTime = 0;

> startTime = System.currentTimeMillis();

>

> return startTime;

> }

>

> public void print(String message, long startTm) {

>

> long endTime = 0;

>

> endTime = System.currentTimeMillis();

> System.out.println(

> message

> +" "

> + (endTime - startTm)/1000.0 + " seconds");

> }

>

>}

>----------

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>

>

>import java.awt.*;

>

>public class TimerTest {

>

> Timer t = new Timer();

>

> TimerTest () {

>

> int Sum = 0;

> long startTm = t.start();

>

> for (int i=0; i<100000; i++)

> {

> Sum += random(255);

> }

>

> t.print(("Test Timer without paint() took "), startTm);

> }

>

> public int random(int r) {

> return (int) (Math.floor(Math.random()*r));

> }

>

> public static void main(String args[]) {

> for(int i=0; i<10; i++)

> {

> TimerTest tt = new TimerTest();

> System.out.println("");

> }

> }

>}

>----------

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>

>

>Attachment converted: RAM Disk:TimerTest.class (????/----) (00000015)

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