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/**
* Copyright (c) 2004 - 2009 Eike Stepper (Berlin, Germany) and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Simon McDuff - initial API and implementation
* Eike Stepper - maintenance
*/
package org.eclipse.net4j.util.concurrent;
/**
* Allow synchronization between many threads for a specific value, e.g.:
*
* <pre>
* MainThread cv.set(1);
* Thread1 cv.acquire(3);
* Thread2 cv.acquire(4);
* Thread3 cv.acquire(100);
* Thread4 cv.acquire(new Object()
* {
* public boolean equals(Object other)
* {
* return other.equals(2) || other.equals(3);
* }
* });
* Thread5 cv.acquire(1);
* ...
* // Thread 1,2,3 and 4 are blocked
* // Thread 5 isn't blocked.
*
* MainThread cv.set(3);
*
* // Thread 1 and 4 are unblocked.
* // Thread 2 and 3 are still blocked.
* </pre>
*
* @author Simon McDuff
* @since 2.0
*/
public final class ConcurrentValue<T>
{
private Object notifier = new Object();
private T value;
public ConcurrentValue(T value)
{
this.value = value;
}
public T get()
{
return value;
}
/**
* Specify the new value.
*/
public void set(T newValue)
{
synchronized (notifier)
{
value = newValue;
notifier.notifyAll();
}
}
/**
* Reevaluate the condition. It is only useful if a thread is blocked at {@link ConcurrentValue#acquire()} and the
* parameter passed changed. {@link ConcurrentValue#acquire()} generates a reevaluation automatically.
*/
public void reevaluate()
{
synchronized (notifier)
{
notifier.notifyAll();
}
}
/**
* Blocking call.
* <p>
* Return when value accept is equal to {@link ConcurrentValue#get()}.
*/
public void acquire(Object accept) throws InterruptedException
{
if (accept == null)
{
throw new IllegalArgumentException("accept == null");
}
synchronized (notifier)
{
while (!accept.equals(value))
{
notifier.wait();
}
}
}
}
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