package threadbook.ch17;

public class BooleanLock extends Object {

private boolean value;

public BooleanLock(boolean initialValue) {

value = initialValue;

}

public BooleanLock() {

this(false);

}

public synchronized void setValue(boolean newValue) {

if ( newValue != value ) {

value = newValue;

notifyAll();

}

}

public synchronized boolean waitToSetTrue(long msTimeout)

throws InterruptedException {

boolean success = waitUntilFalse(msTimeout);

if ( success ) {

setValue(true);

}

return success;

}

public synchronized boolean waitToSetFalse(long msTimeout)

throws InterruptedException {

boolean success = waitUntilTrue(msTimeout);

if ( success ) {

setValue(false);

}

return success;

}

public synchronized boolean isTrue() {

return value;

}

public synchronized boolean isFalse() {

return !value;

}

public synchronized boolean waitUntilTrue(long msTimeout)

throws InterruptedException {

return waitUntilStateIs(true, msTimeout);

}

public synchronized boolean waitUntilFalse(long msTimeout)

throws InterruptedException {

return waitUntilStateIs(false, msTimeout);

}

public synchronized boolean waitUntilStateIs(

boolean state,

long msTimeout

) throws InterruptedException {

if ( msTimeout == 0L ) {

while ( value != state ) {

wait(); // wait indefinitely until notified

}

// condition has finally been met

return true;

}

// only wait for the specified amount of time

long endTime = System.currentTimeMillis() + msTimeout;

long msRemaining = msTimeout;

while ( ( value != state ) && ( msRemaining > 0L ) ) {

wait(msRemaining);

msRemaining = endTime - System.currentTimeMillis();

}

// May have timed out, or may have met value,

// calculate return value.

return ( value == state );

}

}