Using Object.wait(millisec) to simulate sleep

Question

Here\'s a snippet of code that I saw in some code I\'m maintaining.

Object lock = new Object();

synchronized( lock ) 
{
   try
   {
       lock.wait( 50000          


        

Answer 1

Note that there is one key difference in using Object.wait() and Thread.sleep() inside a synchronization block: Thread.sleep() does not release the locked monitor, so no-one else can become the owner of the monitor.

In addition, Object.wait() does not guarantee that the delay indicated will be obeyed strictly. First of all, after the delay passes, the thread may still be waiting for another thread that has become the monitor owner in the meantime; and it may compete with other threads waiting to grab the monitor.

Second, the mythical spurious wake-up, as it is described in the Java 6 API javadoc:

A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup.

Unlikely as it is, every piece of code using Object.wait() should take it into consideration.