Java: How to distinguish between spurious wakeup and timeout in wait()

Question

Here is a case where a thread is waiting for notify() or a timeout. Here a while loop is added to handle spurious wake up.

boolean dosleep = true;
while (do         


        

Answer 1

I believe Locks and Condition will better fit your need in this case. Please check the javadocs for Condition.awaitUntil() - it has an example of usage

Answer 2

You need to keep track of your timeout if you want to distinguish the two cases.

long timeout = 2000;
long timeoutExpires = System.currentTimeMillis() + timeout;
while(dosleep) {
  wait(timeout);
  if(System.currentTimeMillis() >= timeoutExpires) {
    // Get out of loop
    break;
  }
}

That said, denis's recommendation of using the Condition class is the better way to do this.

Answer 3

You could do this:

boolean dosleep = true;
long endTime = System.currentTimeMillis() + 2000;
while (dosleep) {
    try {
        long sleepTime = endTime - System.currentTimeMillis();
        if (sleepTime <= 0) {
            dosleep = false;
            } else {
            wait(sleepTime);
        }
    } catch ...
}

That should work fine in Java 1.4, and it will ensure that your thread sleeps for at least 2000ms.