Why is UncaughtExceptionHandler not called by ExecutorService?

Question

I\'ve stumbled upon a problem, that can be summarized as follows:

When I create the thread manually (i.e. by instantiating java.lang.Thread) the U

Answer 1

Because the exception does not go uncaught.

The Thread that your ThreadFactory produces is not given your Runnable or Callable directly. Instead, the Runnable that you get is an internal Worker class, for example see ThreadPoolExecutor$Worker. Try System.out.println() on the Runnable given to newThread in your example.

This Worker catches any RuntimeExceptions from your submitted job.

You can get the exception in the ThreadPoolExecutor#afterExecute method.