How to shut down all Executors when quitting an application?

Question

According to Brian Goetz\'s Java Concurrency in Practice JVM can\'t exit until all the (nondaemon) threads have terminated, so failing to shut down an Executor could pre

Answer 1

By default, an Executor will create only non-daemon threads. You can override that by supplying the Executor with your own ThreadFactory. Here's an example:

class DaemonThreadFactory implements ThreadFactory {
  public Thread newThread(Runnable r) {
    Thread t = new Thread(r);
    t.setDaemon(true);
    return t;
  }
}

Be cautious, though, because the JVM will exit right away even if these threads are busy doing useful work!