1    package thread; 
2     
3    public class Queues { 
4        private static final int queue_size = 10; 
5        private Object[] queue = 
6                new Object[queue_size]; 
7     
8        private int head = 0; 
9        private int tail = 0; 
10    
11       synchronized public void 
12               enqueue(Object item) { 
13           ++head; 
14           int i = head % queue_size; 
15           queue[i] = item; 
16           this.notify(); 
17       } 
18    
19       synchronized public Object dequeue() { 
20           try { 
21               while (head == tail) { 
22                   this.wait(); 
23               } 
24           } catch (InterruptedException e) { 
25               return null; 
26           } 
27           return queue[++tail % queue_size]; 
28       } 
29    
30       public static void main(String args[]) { 
31           Queues q 
32                   = new Queues(); 
33           q.enqueue(q); 
34           q.enqueue(q); 
35           System.out.println(q); 
36           System.out.println(q.dequeue()); 
37    
38       } 
39   } 
40    
41   class Consumer implements Runnable { 
42       Queues q; 
43    
44       Consumer(Queues _q) { 
45           q = _q; 
46       } 
47    
48       public void run() { 
49           while (true) { 
50               System.out.println( 
51                       (String) q.dequeue()); 
52           } 
53       } 
54   } 
55    
56   class Producer { 
57    
58       public static void main(String args[]) { 
59           Queues q = 
60                   new Queues(); 
61           Thread ct = new Thread(new Consumer(q)); 
62           Producer p = new Producer(); 
63           ct.start(); 
64           q.enqueue("This is my first entry"); 
65           q.enqueue("This is my second entry"); 
66           q.enqueue("This is my third entry"); 
67           q.enqueue("This is my third entry"); 
68           q.enqueue("This is my third entry"); 
69           q.enqueue("This is my third entry"); 
70           q.enqueue("This is my third entry"); 
71           q.enqueue("This is my third entry"); 
72           q.enqueue("This is my third entry"); 
73           q.enqueue("This is my third entry"); 
74           q.enqueue("This is my third entry"); 
75       } 
76   } 
77