AbstractQueuedSynchronizer extends AbstractOwnableSynchronizer implements java.io.Serializable { public final boolean hasQueuedThreads() { return head != tail; } protected  AbstractQueuedSynchronizer(); final void acquire(long arg); final void acquireInterruptibly(long arg); final boolean tryAcquireNanos(long arg, long nanosTimeout); final boolean release(long arg); final void acquireShared(long arg); final void acquireSharedInterruptibly(long arg); final boolean tryAcquireSharedNanos(long arg, long nanosTimeout); final boolean releaseShared(long arg); final boolean hasQueuedThreads(); final boolean hasContended(); final Thread getFirstQueuedThread(); final boolean isQueued(Thread thread); final boolean hasQueuedPredecessors(); final int getQueueLength(); final Collection<Thread> getQueuedThreads(); final Collection<Thread> getExclusiveQueuedThreads(); final Collection<Thread> getSharedQueuedThreads(); String toString(); final boolean owns(ConditionObject condition); final boolean hasWaiters(ConditionObject condition); final int getWaitQueueLength(ConditionObject condition); final Collection<Thread> getWaitingThreads(ConditionObject condition);  }
@Test public void testHasQueuedThreads() { final Mutex sync = new Mutex(); assertFalse(sync.hasQueuedThreads()); sync.acquire(); Thread t1 = newStartedThread(new InterruptedSyncRunnable(sync)); waitForQueuedThread(sync, t1); assertTrue(sync.hasQueuedThreads()); Thread t2 = newStartedThread(new InterruptibleSyncRunnable(sync)); waitForQueuedThread(sync, t2); assertTrue(sync.hasQueuedThreads()); t1.interrupt(); awaitTermination(t1); assertTrue(sync.hasQueuedThreads()); sync.release(); awaitTermination(t2); assertFalse(sync.hasQueuedThreads()); }