Question

I understand that having a thread sucking for elements of a BlockingQueue using the take() method will wait for an element to be available (unless it is interrupted).

I have two questions:

i) Is the thread automatically woken-up as soon as an element becomes available or is there a delay (i.e., the thread checks itself later)?

ii) If there is a delay, does it make sense to wake up the thread (by interrupting it explicitly for example)? I am thinking about latency and performance.

Answer 1

There is no additional delay. The method call returns if a element is available or the thread is interrupted.

Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

Returns:
    the head of this queue 
Throws:
    InterruptedException - if interrupted while waiting

The BlockinQueue is doing this automatically (impl. of ArrayBlockingQueue).

// in add etc.
notEmpty.signal();

// in take()
while(count == 0) 
  notEmpty.await();