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77 lines (64 loc) · 1.5 KB
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package threadbook.ch17;
public class TransitionDetector extends Object {
private boolean value;
private Object valueLock;
private Object falseToTrueLock;
private Object trueToFalseLock;
public TransitionDetector(boolean initialValue) {
value = initialValue;
valueLock = new Object();
falseToTrueLock = new Object();
trueToFalseLock = new Object();
}
public void setValue(boolean newValue) {
synchronized ( valueLock ) {
if ( newValue != value ) {
value = newValue;
if ( value ) {
notifyFalseToTrueWaiters();
} else {
notifyTrueToFalseWaiters();
}
}
}
}
public void pulseValue() {
// Sync on valueLock to be sure that no other threads
// get into setValue() between these two setValue()
// calls.
synchronized ( valueLock ) {
setValue(!value);
setValue(!value);
}
}
public boolean isTrue() {
synchronized ( valueLock ) {
return value;
}
}
public void waitForFalseToTrueTransition()
throws InterruptedException {
synchronized ( falseToTrueLock ) {
falseToTrueLock.wait();
}
}
private void notifyFalseToTrueWaiters() {
synchronized ( falseToTrueLock ) {
falseToTrueLock.notifyAll();
}
}
public void waitForTrueToFalseTransition()
throws InterruptedException {
synchronized ( trueToFalseLock ) {
trueToFalseLock.wait();
}
}
private void notifyTrueToFalseWaiters() {
synchronized ( trueToFalseLock ) {
trueToFalseLock.notifyAll();
}
}
public String toString() {
return String.valueOf(isTrue());
}
}