Mutex.java

/*
 * Copyright 1999-2000 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.awt;

public class Mutex {
    private boolean locked;
    private Thread owner;

    public synchronized void lock() {
        if (locked && Thread.currentThread() == owner) {
            throw new IllegalMonitorStateException();
        }
        do {
            if (!locked) {
                locked = true;
                owner = Thread.currentThread();
            } else {
                try {
                    wait();
                } catch (InterruptedException e) {
                    // try again
                }
            }
        } while (owner != Thread.currentThread());
    }

    public synchronized void unlock() {
        if (Thread.currentThread() != owner) {
            throw new IllegalMonitorStateException();
        }
        owner = null;
        locked = false;
        notify();
    }

    protected boolean isOwned() {
        return (locked && Thread.currentThread() == owner);
    }
}