ArrayBlockingQueue - is it really Concurrent?

Question

Not a single operation of ArrayBlockingQueue is concurrent with any of its other operations; they always take the same lock. Even for the size() method it takes a lock.

 public int size() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return count;
        } finally {
            lock.unlock();
        }
    }

While for the implementation of LinkedBlockingQueue you have two locks: put and take. And for size() it uses AtomicInteger so doesn't need a lock.

So my question is: why is this implementation in the concurrent package - is ArrayBlockingQueue really concurrent?

It can be used in a concurrent setting---that's the point.

Marko Topolnik
– Marko Topolnik

2013-07-10 18:30:52 +00:00
Commented Jul 10, 2013 at 18:30 — Marko Topolnik
– Marko Topolnik, Commented Jul 10, 2013 at 18:30

Duncan Jones · Accepted Answer · 2013-07-10 18:30:44Z

8

ArrayBlockingQueue is in the java.util.concurrent package because multiple threads can use the object concurrently without thread-safety problems.

The ability to use multiple methods at the same time is not what the object is made for.

answered Jul 10, 2013 at 18:30

Duncan Jones

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1 Comment

jtahlborn Over a year ago

I would add that the "concurrent" package is a colleciton of utils for building concurrent applications. the utils are all "thread-safe". Some are more intrinsically "concurrent" than others.

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