Thread Pooling (was Efficient CPU usage with recursively parallelizable problem)

"Mike Schilling" <>
Sat, 17 Oct 2009 19:00:08 -0700
markspace wrote:

chucky wrote:

This isn't directly related to my original post, but I was
if the implementation of thread pool needs some special compiler
support. I can't see in the java.lang.Thread API how to use the
thread for execution of different tasks.

No, I don't think it does. Imagine a sub-class of of Thread that
something like this:

class PoolThread extends Thread {

  volatile Runnable task;
  volatile boolean done = true;

  synchronized public void start() {
    for( ;; ) {
      while( task == null ) {
      done = false;
      try {;
      finally {
        done = true;

Now you have a Thread class that can be re-used. If "done" is true,
you can see if the thread is still running (if it is, no errors were
thrown). If the thread is running and the done flag is set, then we
can reuse the task, set it to a different task, and notifyAll() on
thread to wake it up and cause it to execute the next task.

If the task throws an exception, then the thread will stop, but I
think that's required. Normally after your thread does throw an
exception, it's replaced, not reused.

Why not catch the exception (logging it, so as not to lose it) and
re-use the thread?

Somewhat tangentially, I've never understood why java.util.Timer was
designed to stop running TimerTasks if one throws an uncaught
exception. My response to that was to write a wrapper class for the
TimerTask that catches and logs the exception before returning back to
the Timer's task-running logic.

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