How to solve this race condition

Question

Hi there,
the following code was taken from an official Java Tutorial at http://java.sun.com/docs/books/tutorial/essential/threads/synchronization.html but it's bugy 'cause it's creating race conditions I cannot handle.
// this is the consumer
// it tries to get the content of cubbyhole
// but as soon as "available" becomes "false"
// the content can change
public synchronized int get() {
        while (available == false) {
            try {
                wait();
            } catch (InterruptedException e) { }
        available = false; // <-- the producer can access the cubbyhole
        notifyAll(); // the producer is being notified (wake up)
        return contents;
    }Imagine the scheduler interrupts the consumer just after the "notifyAll()" method (race condition). The producer can access the cubbyhole (available = false) and store a new value in it. Due to the fact that the cubbyhole is a reference the "return contents" command in the consumer will now return the new (overwritten) value. This code definitely won't work. The only way it works is to clone (!) the current "contents" in a separate variable BEFORE awaking the producer and enabling it to make changes.
I had serious troubles in using the wait() methods and like to know your oppinions/experiences about that.
Thx for reading.
90210

Answer 1

I'm not going to bother looking at that tutorial, but I'd venture to guess that you are making a false assumption. Since get() is synchronized, no other thread can acquire a lock to the object being synchronized on while this method is changing the value of 'available' to false. But without seeing the context of what those other threads might be doing, it's hard to tell if you really have a valid claim or not (that it's 'buggy'). But 99.99999% of the time, its your own mistake/misinformation/invalid analysis.