calling Thread.sleep() from synchronized context in Java

java multithreading synchronized thread-sleep
Anand picture Anand · May 19, 2012 · Viewed 14.3k times · Source

I have read that Thread.sleep() will pause the currently running thread for the time specified after which it goes back to runnable state waiting for it's turn to run.

Also, if called from synchronized context, sleep() doesn't release the lock it holds. So I was wondering when it will release the lock. If the thread, put on sleep, never gets the chance to run so it will always keep the lock with itself and then how other threads get to enter synchronized methods/block.

I am not sure if I am asking valid question. But please help me out.

Answer

NPE picture NPE · May 19, 2012

So I was wondering when it will release the lock.

It will release the lock upon exit from the synchronized block, and not earlier.

If the thread, put on sleep, never gets the chance to run so it will always keep the lock with itself and then how other threads get to enter synchronized methods/block.

Quite simply, other threads will not be able to enter code that's synchronized on the same object that the sleeping thread.

To summarize, calling Thread.sleep() from a synchronized block is likely not a good idea.

Related questions

What does 'synchronized' mean?

I have some questions regarding the usage and significance of the synchronized keyword. What is the significance of the synchronized keyword? When should methods be synchronized? What does it mean programmatically and logically?

Read More
Is there an advantage to use a Synchronized Method instead of a Synchronized Block?

Can any one tell me the advantage of synchronized method over synchronized block with an example?

Read More
Java synchronized method lock on object, or method?

If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside …

Read More