multithreading - Java performance issue with Thread.sleep()

Question

Inline Java IDE hint states, "Invoking Thread.sleep in loop can cause performance problems." I can find no elucidation elsewhere in the docs re. this statement.

Why? How? What other method might there be to delay execution of a thread?

Answer 1

It is not that Thread.sleep in a loop itself is a performance problem, but it is usually a hint that you are doing something wrong.

while(! goodToGoOnNow()) {
   Thread.sleep(1000);
}

Use Thread.sleep only if you want to suspend your thread for a certain amount of time. Do not use it if you want to wait for a certain condition.

For this situation, you should use wait/notify instead or some of the constructs in the concurrency utils packages.

Polling with Thread.sleep should be used only when waiting for conditions external to the current JVM (for example waiting until another process has written a file).