/** compareAndSet succeeds in changing value if equal to expected else fails */
public void testCompareAndSet() {
AtomicLong ai = new AtomicLong(1);
assertTrue(ai.compareAndSet(1, 2));
assertTrue(ai.compareAndSet(2, -4));
assertEquals(-4, ai.get());
assertFalse(ai.compareAndSet(-5, 7));
assertFalse((7 == ai.get()));
assertTrue(ai.compareAndSet(-4, 7));
assertEquals(7, ai.get());
}
/** compareAndSet in one thread enables another waiting for value to succeed */
public void testCompareAndSetInMultipleThreads() {
final AtomicLong ai = new AtomicLong(1);
Thread t =
new Thread(
new Runnable() {
public void run() {
while (!ai.compareAndSet(2, 3)) Thread.yield();
}
});
try {
t.start();
assertTrue(ai.compareAndSet(1, 2));
t.join(LONG_DELAY_MS);
assertFalse(t.isAlive());
assertEquals(ai.get(), 3);
} catch (Exception e) {
unexpectedException();
}
}