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public class InterruptibleSyncBlock extends Object {
private Object longLock;
private BooleanLock busyLock;
public InterruptibleSyncBlock() {
longLock = new Object();
busyLock = new BooleanLock(false);
}
public void doStuff() throws InterruptedException {
print("about to try to get exclusive access " + "to busyLock");
busyLock.waitToSetTrue(0);
try {
print("about to try to get exclusive access " + "to longLock");
synchronized (longLock) {
print("got exclusive access to longLock");
try {
Thread.sleep(10000);
} catch (InterruptedException x) {
// ignore
}
print("about to relinquish exclusive access " + "to longLock");
}
} finally {
print("about to free up busyLock");
busyLock.setValue(false);
}
}
private static void print(String msg) {
String name = Thread.currentThread().getName();
System.err.println(name + ": " + msg);
}
private static Thread launch(final InterruptibleSyncBlock sb, String name) {
Runnable r = new Runnable() {
public void run() {
print("in run()");
try {
sb.doStuff();
} catch (InterruptedException x) {
print("InterruptedException thrown " + "from doStuff()");
}
}
};
Thread t = new Thread(r, name);
t.start();
return t;
}
public static void main(String[] args) {
try {
InterruptibleSyncBlock sb = new InterruptibleSyncBlock();
Thread t1 = launch(sb, "T1");
Thread.sleep(500);
Thread t2 = launch(sb, "T2");
Thread t3 = launch(sb, "T3");
Thread.sleep(1000);
print("about to interrupt T2");
t2.interrupt();
print("just interrupted T2");
} catch (InterruptedException x) {
x.printStackTrace();
}
}
}
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 );
}
}
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