1  /** 

  2      A first-in, first-out bounded collection of objects. 

  3  */ 

  4  public class BoundedQueue<E>

  5  { 

  6     /** 

  7         Constructs an empty queue. 

  8         @param capacity the maximum capacity of the queue 

  9     */ 

 10     public BoundedQueue(int capacity) 

 11     { 

 12        elements = new Object[capacity]; 

 13        head = 0; 

 14        tail = 0; 

 15        size = 0;

 16     } 

 17  

 18     /** 

 19         Removes the object at the head. 

 20         @return the object that has been removed from the queue

 21     */ 

 22     public synchronized E remove() 

 23           throws InterruptedException

 24     { 

 25        while (size == 0) wait();

 26        @SuppressWarnings("unchecked") E r = (E) elements[head]; 

 27        head++;

 28        size--;

 29        if (head == elements.length) 

 30           head = 0; 

 31        notifyAll();

 32        return r; 

 33     } 

 34  

 35     /** 

 36         Appends an object at the tail. 

 37         @param newValue the object to be appended 

 38     */ 

 39     public synchronized void add(E newValue) 

 40           throws InterruptedException

 41     { 

 42        while (size == elements.length) wait();

 43        elements[tail] = newValue; 

 44        tail++;

 45        size++;

 46        if (tail == elements.length) 

 47           tail = 0; 

 48        notifyAll();

 49     } 

 50  

 51     private Object[] elements; 

 52     private int head; 

 53     private int tail; 

 54     private int size;

 55  }