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Java example source code file (ConditionLock.java)

This example Java source code file (ConditionLock.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

conditionlock, interruptedexception, lock

The ConditionLock.java Java example source code

/*
 * Copyright (c) 1994, 2005, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.misc;

/**
 * ConditionLock is a Lock with a built in state variable.  This class
 * provides the ability to wait for the state variable to be set to a
 * desired value and then acquire the lock.<p>
 *
 * The lockWhen() and unlockWith() methods can be safely intermixed
 * with the lock() and unlock() methods. However if there is a thread
 * waiting for the state variable to become a particular value and you
 * simply call Unlock(), that thread will not be able to acquire the
 * lock until the state variable equals its desired value. <p>
 *
 * @author      Peter King
 */
public final
class ConditionLock extends Lock {
    private int state = 0;

    /**
     * Creates a ConditionLock.
     */
    public ConditionLock () {
    }

    /**
     * Creates a ConditionLock in an initialState.
     */
    public ConditionLock (int initialState) {
        state = initialState;
    }

    /**
     * Acquires the lock when the state variable equals the desired state.
     *
     * @param desiredState the desired state
     * @exception  java.lang.InterruptedException if any thread has
     *               interrupted this thread.
     */
    public synchronized void lockWhen(int desiredState)
        throws InterruptedException
    {
        while (state != desiredState) {
            wait();
        }
        lock();
    }

    /**
     * Releases the lock, and sets the state to a new value.
     * @param newState the new state
     */
    public synchronized void unlockWith(int newState) {
        state = newState;
        unlock();
    }
}

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