Java wait（）不会抛出InterruptedException

Question

I have an object on thread A that is calling wait() while another object on thread B does some work then calls thread A 's object's notify() . Thread A then performs some post-processing.

My problem is pretty straightforward:

synchronized(this)
{
    while(!flag)
    {
        try
        {
            wait();
            getLogger().info("No longer waiting");
        }
        catch (InterruptedException ie)
        {
            getLogger().info("Wait threw InterruptedException");
        }
    }
}

Results in an info message of "No longer waiting" instead of "Wait threw InterruptedException".

I am confused, because of this ( http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Object.html#wait() ):

Throws:

InterruptedException - if another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.

Why am I getting odd behavior?

Thanks.

Answer 1

When a thread waits using wait() , he actually waits for notify() . So once notify() has been called by the other thread, this thread will continue, if you will call interrupt() , you would get the exception.

Also, from the documents you linked to:

Causes current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object

notify releases the thread from the lock.

InterruptedException - if another thread interrupted the current thread before or while the current thread was waiting for a notification.

Answer 2

notify() does not make wait() throw InterruptedException . notify() let wait() continue the normal program flow.

Answer 3

notify() is not an abnormal termintation for a thread that is wait() -ing. You'd get the exception if, for instance, the thread was terminated before notify() was called - not as a result of notify() being called. The thread hasn't been interrupted - it's been awoken.

Answer 4

Note that you have a bug in that code. Wait should always be invoked in a loop, and check a condition after waking up.

wait can be awaken by a spurious wakeup. See the javadoc wait()