Question

I have a class with a function which is synchronized like so:

public synchronized void enqueue(int number) {...}

In my program I have several threads running all wanting to use this function on a specific object of the class. What I would like to happen is for the threads to simply try using the function and if it is locked to not wait on it simply skip running that function.

Can this be done without using the Java.util.concurency library and only using syncronization primatives?

The restriction of not using concurrency is not optional

Answer 1

I like the AtomicInteger solution, but of course AtomicInteger is part of the concurrency package. You can follow the same principle (with lower efficiency, though) with the following simple code:

private boolean locked = false;

public void enqueue(int number) {
    synchronized (this) {
        if (locked) {
            return;
        }
        locked = true;
    }

    try {
        // Synchronized goodness goes here.
    } finally {
        synchronized (this) {
            locked = false;
        }
    }
}