Java tutorial
/* * Funambol is a mobile platform developed by Funambol, Inc. * Copyright (C) 2003 - 2007 Funambol, Inc. * * This program is free software; you can redistribute it and/or modify it under * the terms of the GNU Affero General Public License version 3 as published by * the Free Software Foundation with the addition of the following permission * added to Section 15 as permitted in Section 7(a): FOR ANY PART OF THE COVERED * WORK IN WHICH THE COPYRIGHT IS OWNED BY FUNAMBOL, FUNAMBOL DISCLAIMS THE * WARRANTY OF NON INFRINGEMENT OF THIRD PARTY RIGHTS. * * This program 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 General Public License for more * details. * * You should have received a copy of the GNU Affero General Public License * along with this program; if not, see http://www.gnu.org/licenses or write to * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, * MA 02110-1301 USA. * * You can contact Funambol, Inc. headquarters at 643 Bair Island Road, Suite * 305, Redwood City, CA 94063, USA, or at email address info@funambol.com. * * The interactive user interfaces in modified source and object code versions * of this program must display Appropriate Legal Notices, as required under * Section 5 of the GNU Affero General Public License version 3. * * In accordance with Section 7(b) of the GNU Affero General Public License * version 3, these Appropriate Legal Notices must retain the display of the * "Powered by Funambol" logo. If the display of the logo is not reasonably * feasible for technical reasons, the Appropriate Legal Notices must display * the words "Powered by Funambol". */ import java.util.Stack; /** * A multithreaded queue used for * implementing producer-consumer style threading patterns. * Multiple threads can wait for runnable objects being added * to the queue while other threads add to the queue. */ public class Queue { private Stack tasks = new Stack(); private long defaultTimeout = 100; public Queue() { } /** * Returns the current number of runnable objects in the queue */ public synchronized int size() { return tasks.size(); } /** * adds a runnable object to the end of the queue. * At least one thread will be notified. */ public synchronized void add(Object runnable) { tasks.push(runnable); notifyAll(); } /** * Removes the first runnable object from the queue, blocking until one is available. */ public synchronized Object remove() { while (true) { Object runnable = removeNoWait(); if (runnable != null) { return runnable; } try { wait(defaultTimeout); } catch (InterruptedException e) { e.printStackTrace(); } } } /** * Removes the first runnable object from the queue without blocking. * This method will return immediately with an item from the queue or null. * @return the first runnable object removed from the queue or null if the * queue is empty */ public synchronized Object removeNoWait() { if (!tasks.empty()) { return tasks.pop(); } else { return null; } } }