1    package thread; 
2     
3    public class RaceThread extends Thread { 
4     
5        public void run() { 
6            while (true) { 
7                printThreadGroups(); 
8                try { 
9                    Thread.sleep(10000); 
10               } catch (InterruptedException e) { 
11               } 
12    
13           } 
14       } 
15    
16    
17       public ThreadGroup getSystemThreadGroup() { 
18    
19           ThreadGroup systemThreadGroup; 
20           ThreadGroup parentThreadGroup; 
21    
22           systemThreadGroup = Thread.currentThread().getThreadGroup(); 
23    
24           while ((parentThreadGroup = systemThreadGroup.getParent()) != null) 
25               systemThreadGroup = parentThreadGroup; 
26    
27           return systemThreadGroup; 
28       } 
29    
30    
31       public ThreadGroup[] getThreadGroupsArray() { 
32    
33           ThreadGroup systemThreadGroup = getSystemThreadGroup(); 
34    
35           int numberOfGroups = systemThreadGroup.activeGroupCount() + 1; 
36    
37           ThreadGroup threadGroupsArray[] = new 
38                   ThreadGroup[numberOfGroups]; 
39    
40           systemThreadGroup.enumerate(threadGroupsArray); 
41    
42           threadGroupsArray[numberOfGroups] = systemThreadGroup; 
43    
44           return threadGroupsArray; 
45       } 
46    
47       public Thread[] getThreadsArray() { 
48    
49           ThreadGroup systemThreadGroup = getSystemThreadGroup(); 
50    
51           Thread threadsArray[] = new Thread[systemThreadGroup.activeCount()]; 
52           systemThreadGroup.enumerate(threadsArray); 
53    
54           return threadsArray; 
55       } 
56    
57       public void printThreadGroups() { 
58           getSystemThreadGroup().list(); 
59       } 
60    
61       public void printThreads() { 
62           Thread[] threadsArray = getThreadsArray(); 
63           for (int i = 0; i < threadsArray.length; i++) 
64               System.out.println(threadsArray[i]); 
65       } 
66    
67       public void printThreadsAndGroups() { 
68           System.out.println("The threads are:"); 
69           printThreads(); 
70           System.out.println("The groups are:"); 
71           printThreadGroups(); 
72       } 
73    
74   }