/*

 * 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;

/**

 * The Lock class provides a simple, useful interface to a lock.

 * Unlike monitors which synchronize access to an object, locks

 * synchronize access to an arbitrary set of resources (objects,

 * methods, variables, etc.). <p>

 *

 * The programmer using locks must be responsible for clearly defining

 * the semantics of their use and should handle deadlock avoidance in

 * the face of exceptions. <p>

 *

 * For example, if you want to protect a set of method invocations with

 * a lock, and one of the methods may throw an exception, you must be

 * prepared to release the lock similarly to the following example:

 * <pre>

 *      class SomeClass {

 *          Lock myLock = new Lock();

 *          void someMethod() {

 *              myLock.lock();

 *              try {

 *                  StartOperation();

 *                  ContinueOperation();

 *                  EndOperation();

 *              } finally {

 *                  myLock.unlock();

 *              }

 *          }

 *      }

 * </pre>

 *

 * @author      Peter King

 */

public

class Lock {

    private boolean locked = false;

    /**

     * Create a lock, which is initially not locked.

     */

    public Lock () {

    }

    /**

     * Acquire the lock.  If someone else has the lock, wait until it

     * has been freed, and then try to acquire it again.  This method

     * will not return until the lock has been acquired.

     *

     * @exception  java.lang.InterruptedException if any thread has

     *               interrupted this thread.

     */

    public final synchronized void lock() throws InterruptedException {

        while (locked) {

            wait();

        }

        locked = true;

    }

    /**

     * Release the lock.  If someone else is waiting for the lock, the

     * will be notitified so they can try to acquire the lock again.

     */

    public final synchronized void unlock() {

        locked = false;

        notifyAll();

    }

}