Multithreading: BlockingQueue.poll with a timeout avoids waiting forever

poll() with no arguments returns null immediately on an empty queue, while poll(timeout, unit) waits up to that long for an item before giving up. Both are safer than take(), which would block indefinitely.

Code

BlockingQueue<String> queue = new LinkedBlockingQueue<>();
String immediate = queue.poll();
String afterWait;
try {
    afterWait = queue.poll(30, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
    afterWait = null;
}
System.out.println("Poll on an empty queue (no wait): " + immediate);
System.out.println("Poll with a timeout, still empty: " + afterWait);

Output

Poll on an empty queue (no wait): null
Poll with a timeout, still empty: null