/*
* 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();
}
}