queue.java

Java Communicating Agents是一个用于开发网络反应式信息agent的框架

/*
 * $Source: /home/data/cvsroot/src/jacomma/util/Queue.java,v $
 * $Revision: 1.7 $
 * $Date: 2000/10/28 20:09:08 $
 *
 * This file is part of the jacomma framework
 * Copyright (c) 2000 	Dimitrios Vyzovitis
 *			mailto:[e-mail]
 *			
 *
 *			
 *			
 *			
 *
 *	This library is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU Library General Public License as published by
 *	the Free Software Foundation; either version 2 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 Library General Public License for more details.
 *
 *	You should have received a copy of the GNU Library 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
 */

package jacomma.util;

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

/**
 * TBA
 **/
public class Queue {
	
	public static final int DEFAULT_INITIAL_SIZE = 10;
	
	protected List que_;

	public Queue() {
		this( DEFAULT_INITIAL_SIZE );
	}
	
	public Queue( int isz ) {
		que_ = new ArrayList( isz );
	}


	public synchronized void put( Object obj ) {
		que_.add( obj );
		notifyAll();
	}
	
	public synchronized void signal() { notifyAll(); }

	public synchronized Object get() throws InterruptedException {
		Object obj = null;
		for ( obj = try_get(); obj == null; obj = try_get() ) wait();
		
		return obj;
	}
	
	public synchronized Object try_get() {
		if ( que_.isEmpty() )
			return null;
		else
			return que_.remove( 0 );
	}
	
	public synchronized Object get( Object test ) throws InterruptedException {
		Object m = null;
		for ( m = try_get( test ); m == null; m = try_get( test ) ) wait();
		
		return m;
	}

	public synchronized Object try_get( Object test ) {
		for( Iterator it = que_.iterator();
			 it.hasNext(); ) {
			Object  next = it.next();
			if ( test.equals( next ) ) {
				que_.remove( next );
				return next;
			}
		}
		
		return null;
	}

	public synchronized Object try_accept( Visitor v ) {
		if ( !v.canVisit( List.class ) || que_.isEmpty() ) return null;
		else return v.visit( que_ );
	}
	
	public synchronized Object accept( Visitor v ) throws InterruptedException {
		if ( v.canVisit( List.class ) ) {
			while( que_.isEmpty() ) wait();
			return v.visit( que_ );
		} else return null;
	}

}