hasQueuedPredecessors

Queries whether any threads have been waiting to acquire longer than the current thread.

An invocation of this method is equivalent to (but may be more efficient than):

 `getFirstQueuedThread() != Thread.currentThread()
&& hasQueuedThreads()`

Note that because cancellations due to interrupts and timeouts may occur at any time, a true return does not guarantee that some other thread will acquire before the current thread. Likewise, it is possible for another thread to win a race to enqueue after this method has returned false, due to the queue being empty.

This method is designed to be used by a fair synchronizer to avoid AbstractQueuedSynchronizer.html#barging. Such a synchronizer's .tryAcquire method should return false, and its .tryAcquireShared method should return a negative value, if this method returns true (unless this is a reentrant acquire). For example, the tryAcquire method for a fair, reentrant, exclusive mode synchronizer might look like this:

 `protected boolean tryAcquire(int arg) {
if (isHeldExclusively()) {
// A reentrant acquire; increment hold count
return true;
} else if (hasQueuedPredecessors()) {
return false;
} else {
// try to acquire normally
}
}`