boundedqueue.java

P2P协议GUNTELLA的java源代码

/*
 * Copyright (C) 2000-2001  Ken McCrary
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Email: [e-mail]
 */
package com.kenmccrary.jtella.util;

import java.util.LinkedList;

/**
 *  A Queue supporting standard enqueue/dequeue operations
 *  with a maximum permitted size. Having a maximum size
 *  guards against unrestricted memory usage
 *
 */
public class BoundedQueue extends java.lang.Object 
{
  private int maxSize;
  private LinkedList queue;
  
  /**
   *  Constructs a <code>BoundedQueue</code> with a max size
   *
   *  @param max size for queue
   */
  public BoundedQueue(int maxSize) 
  {
    this.maxSize = maxSize;
    queue = new LinkedList();
  }

  /**
   * Enqueue an object
   *
   * @return true if enqueue worked, false if queue is full
   */
  public synchronized boolean enqueue(Object o)
  {
    if ( queue.size() > maxSize )
    {    
      return false;  
    }    
    
    queue.add(o);
    return true;
  }
  
  /**
   * Removes an object from the queue
   *
   */
  public synchronized Object dequeue()
  {
      return queue.remove(0);
  }    
  
  /**
   *  Check if the queue is empty
   *
   *  @retur true if empty, false otherwise
   */
  public synchronized boolean empty()
  {
    return queue.size() == 0;  
  }    
}