cache.java

myjxta是用jxta开发的一个p2p通讯软件 有聊天 文件共享 视频3大功能 界面采用swing

/*
*  Copyright (c) 2001 Sun Microsystems, Inc.  All rights
*  reserved.
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions
*  are met:
*
*  1. Redistributions of source code must retain the above copyright
*  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 discalimer 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 ackndiowledgment:
*  "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.
*
*  5. Products derived from this software may not be called "JXTA",
*  nor may "JXTA" appear in their name, without prior written
*  permission of Sun.
*
*  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
*  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
*  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
*  DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
*  ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
*  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
*  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
*  USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
*  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
*  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
*  OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
*  SUCH DAMAGE.
*  ====================================================================
*
*  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: Cache.java,v 1.6 2007/05/28 22:00:51 nano Exp $
*/

package net.jxta.myjxta.dialog;

import net.jxta.myjxta.util.Group;
import net.jxta.protocol.PipeAdvertisement;
import net.jxta.util.JxtaBiDiPipe;

import java.util.HashMap;

/**
 * Dialog primitive cache.
 *
 * @author james todd [gonzo at jxta dot org]
 * @version $Id: Cache.java,v 1.6 2007/05/28 22:00:51 nano Exp $
 */

class Cache {

    private static HashMap<Group, Cache> caches = null;
    private static final Object lock = new Object();

    private HashMap<PipeAdvertisement, JxtaBiDiPipe> cache = null;

    public static Cache getCache(Group g) {
        Cache c = caches != null ? caches.get(g) : null;

        if (c == null) {
            synchronized (lock) {
                if (caches == null) {
                    caches = new HashMap<Group, Cache>();
                }

                caches.put(g, c = new Cache());
            }
        }

        return c;
    }

    public JxtaBiDiPipe get(PipeAdvertisement pa) {
        return this.cache != null ? this.cache.get(pa) : null;
    }

    public JxtaBiDiPipe put(PipeAdvertisement pa, JxtaBiDiPipe p) {
        if (this.cache == null) {
            this.cache = new HashMap<PipeAdvertisement, JxtaBiDiPipe>();
        }

        return this.cache.put(pa, p);
    }

    public void clear() {
        if (this.cache != null) {
            this.cache.clear();

            this.cache = null;
        }
    }
}