producerbiasedqueue.java

jxta平台的开发包

/*
 *  Copyright (c) 2001-2002 Sun Microsystems, Inc.  All rights reserved.
 *
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 *  notice, this list of conditions and the following disclaimer.
 *
 *  2. Redistributions in binary form must reproduce the above copyright
 *  notice, this list of conditions and the following disclaimer in
 *  the documentation and/or other materials provided with the
 *  distribution.
 *
 *  3. The end-user documentation included with the redistribution,
 *  if any, must include the following acknowledgment:
 *  "This product includes software developed by the
 *  Sun Microsystems, Inc. for Project JXTA."
 *  Alternately, this acknowledgment may appear in the software itself,
 *  if and wherever such third-party acknowledgments normally appear.
 *
 *  4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *  not be used to endorse or promote products derived from this
 *  software without prior written permission. For written
 *  permission, please contact Project JXTA at http://www.jxta.org.
 *
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 *  ====================================================================
 *
 *  This software consists of voluntary contributions made by many
 *  individuals on behalf of Project JXTA.  For more
 *  information on Project JXTA, please see
 *  <http://www.jxta.org/>.
 *
 *  This license is based on the BSD license adopted by the Apache Foundation.
 *
 *  $Id: ProducerBiasedQueue.java,v 1.6 2006/02/13 23:24:25 bondolo Exp $
 */

package net.jxta.impl.util;

import org.apache.log4j.Logger;
import org.apache.log4j.Level;

import java.util.List;
import java.util.ArrayList;

import net.jxta.impl.util.TimeUtils;

/**
 *  A queue who's implementation is biased towards effciency in adding elements
 *  to the queue.
 *
 *  @deprecated Please convert all code to use the java.util.concurrent BlockingQueue instead.
 *
 **/
public class ProducerBiasedQueue extends UnbiasedQueue {
    
    /**
     *  Log4J
     **/
    private static final Logger LOG = Logger.getLogger(ProducerBiasedQueue.class.getName());
    
    /**
     * Default constructor. 100 element FIFO queue which drops oldest element
     * when full.
     */
    public ProducerBiasedQueue() {
        this( DEFAULT_MAX_OBJECTS, DROP_OLDEST_OBJECT );
    }
    
    /**
     * Full featured constructor for creating a new ConsumerBiasedQueue.
     *
     * @param size    Queue will be not grow larger than this size. Use
     *    Integer.MAX_VALUE for "unbounded" queue size.
     * @param dropOldest  Controls behaviour of element insertion when the queue is
     * full. If "true" and the queue is full upon a push operation then the
     * oldest element will be dropped to be replaced with the element currently
     * being pushed. If "false" then then newest item will be dropped.
     */
    public ProducerBiasedQueue(int size, boolean dropOldest) {
        super( size, dropOldest, new ArrayList() );
    }
    
    /**
     *  Flush the queue of all pending objects.
     **/
    public void clear() {
        synchronized( queue ) {
            super.clear();
        }
    }
    
    public boolean push( Object obj ) {
        synchronized( queue ) {
            boolean pushed;
            pushed = super.push( obj );
            queue.notify(); // inform someone who is waiting. we dont have to tell everyone though.
            return pushed;
        }
    }
    
     /*  The pop methods of this queue, unlike the "push" method. This creates a
      *  bottleneck for producers seperate from the primary lock on the "queue"
      *  member. This reduces contention on the primary lock which benefits users
      *  who are popping items from the queue (Consumers).
      *
      */
    
    /**
     * Return next obj in the queue if there is one.
     *
     * @return Object, null if the queue is empty
     **/
    public synchronized Object pop() {
        synchronized( queue ) {
            return super.pop();
        }
    }
    
    /**
     * Gets a Object from the queue. If no Object is immediately available,
     * then wait the specified amount of time. Per Java convention, a timeout
     * of zero (0) means wait an infinite amount of time. Negative values mean
     * do not wait at all.
     *
     * @param timeout amount of time to wait in milliseconds for an object to
     * be available. Per Java convention, a timeout of zero (0) means wait an
     * infinite amount of time. Negative values mean do not wait at all.
     * @return The next object in the queue.
     * @throws InterruptedException    if the operation is interrupted before
     *     the timeout interval is completed.
     */
    public synchronized Object pop( long timeout ) throws InterruptedException {
        synchronized( queue ) {
            return super.pop( timeout );
        }
    }
    
    /**
     *  Returns an array of objects, possibly empty, from the queue.
     *
     *  @param maxObjs  the maximum number of items to return.
     *  @return an array of objects, possibly empty containing the returned
     *  queue elements.
     **/
    public synchronized Object [] popMulti( int maxObjs ) {
        synchronized( queue ) {
            return super.popMulti( maxObjs );
        }
    }
    
    /**
     *  Set how many objects this queue may store. Note that if there are more
     *  objects already in the queue than the specified amount then the queue
     *  will retain its current capacity.
     *
     *  @param maxObjs  The number of objects which the queue must be able to
     *  store.
     **/
    public void setMaxQueueSize( int maxObjs ) {
        synchronized ( queue ) {
            super.setMaxQueueSize( maxObjs );
        }
    }
    
    /**
     *  Return the number of elements currently in the queue. This method is
     *  useful for statistical sampling, but should not be used to determine
     *  program logic due to the multi-threaded behaviour of these queues. You
     *  should use the return values and timeout behaviour of the push() and
     * pop() methods to regulate how you use the queue.
     *
     *  @return the number of elements currently in the queue. Be warned that
     *  even two sequential calls to this method may return different answers
     *  due to activity on other threads.
     *
     **/
    public int getCurrentInQueue() {
        synchronized ( queue ) {
            return super.getCurrentInQueue();
        }
    }
    
    /**
     *  Return the average number of elements in the queue at Enqueue time.
     *
     *  @return average number of elements which were in the queue at during all
     *  of the "push" operations which returned a "true" result. Does not
     *  include the item being pushed. If no elements have ever been enqueued
     *  then "NaN" will be returned.
     **/
    public double getAvgInQueueAtEnqueue() {
        synchronized( queue ) {
            return super.getAvgInQueueAtEnqueue();
        }
    }
    
    /**
     *  Return the average number of elements in the queue at dequeue time.
     *
     *  @return average number of elements which were in the queue at during all
     *  of the "pop" operations which returned a non-null result. Includes the
     * item being "pop"ed in the average. If no elements have ever been dequeued
     *  then "NaN" will be returned.
     **/
    public double getAvgInQueueAtDequeue() {
        synchronized( queue ) {
            return super.getAvgInQueueAtDequeue();
        }
    }
}