/*
* 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 [email protected].
*
* 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;
}
}
}
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