Passing a work item between threads (Java)

Question

I have two threads. The producer is producing pieces of data (String objects), where the consumer processes these strings. The catch is that my application only needs the most recent data object to be processed. In other words, if the producer managed to produce two strings "s1" and then "s2" then I want the consumer to process only "s2". "s1" can be safely discarded.

Of course there's no problem implementing a class that realizes this behavior, but I want to use a standard mechanism from java.util.concurrent (if such a mechanism exists). Note that SynchronousQueue is not a good solution: the consumer will block when enqueueing "s1" and will not get the chance to produce "s2".

(In short, I am looking for a single-element collection with a blocking remove operation and a non-blocking set operation)

Any ideas?

Answer 1

I think your best answer is probably to use ArrayBlockingQueue, where the producer (you only have one producer, right?) removes any existing element before adding the new element.

Sure, there are race conditions in this implementation: the consumer could start processing an element just before the producer removes it. But those race conditions will always exist, no matter what data structure you use.