CompletionMonitor.java from DrJava at Krugle
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/*BEGIN_COPYRIGHT_BLOCK*
PLT Utilities BSD License
Copyright (c) 2007 JavaPLT group at Rice University
All rights reserved.
Developed by: Java Programming Languages Team
Rice University
http://www.cs.rice.edu/~javaplt/
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package edu.rice.cs.plt.concurrent;
import static edu.rice.cs.plt.debug.DebugUtil.debug;
/**
* Enables threads to communicate with each other by signaling. Typically, this communication
* concerns a task which one thread must complete before other threads can proceed.
*/
public class CompletionMonitor {
private volatile boolean _signal;
/** Create an unsignalled completion monitor. */
public CompletionMonitor() { _signal = false; }
/**
* Create a completion monitor in the given initial state. If signalled is {@code true}, invocations of
* {@link #ensureSignalled} will not block until {@link #reset} is invoked.
*/
public CompletionMonitor(boolean signalled) { _signal = signalled; }
/** Returns whether the flag is currently set */
public boolean isSignalled() { return _signal; }
/** Revert to the unsignalled state */
public void reset() { _signal = false; }
/** Sets the state to signalled and alerts all blocked threads */
synchronized public void signal() {
_signal = true;
this.notifyAll();
}
/** Ensures that the monitor has been signalled before continuing. Blocks if necessary. */
synchronized public void ensureSignalled() throws InterruptedException {
while (!_signal) { this.wait(); }
}
/**
* Ensures that the monitor has been signalled before continuing. Blocks if necessary. If the wait is interrupted,
* returns {@code false}.
*/
public boolean attemptEnsureSignalled() {
try { ensureSignalled(); return true; }
catch (InterruptedException e) { return false; }
}
}
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