How to catch exceptions in FutureTask

Question

After finding that FutureTask running in a Executors.newCachedThreadPool() on Java 1.6 (and from Eclipse) swallows exceptions in the Runnable

Answer 1

There are three standard ways and one improvised way. 1. use UncaughtExceptionHandler, set the UncaughtExceptionHandler for the created thread as

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
            public void uncaughtException(Thread t, Throwable ex) {..}}

*But the limitation is it catches the exception thrown by thread but in case of future task, it is swallowed. 2. use afterExecute after making a custom threadpoolexecutor with hook that has been provided specially for this purpose. Looking through the code of ThreadpoolExecutor, via submit > execute (there is a workQueue, workQueue.offer), the tasks are added to the work queue

   final void runWorker(Worker arg0) {
  Thread arg1 = Thread.currentThread();
  Runnable arg2 = arg0.firstTask;
  ..
     while(arg2 != null || (arg2 = this.**getTask()**) != null) {
        arg0.lock();
        ..
        try {
           this.beforeExecute(arg1, arg2);
           Object arg4 = null;
           try {
              arg2.run();
           } catch (RuntimeException arg27) {
             ..
           } finally {
              this.**afterExecute**(arg2, (Throwable)arg4);
           }

  }

getTask() {..
 this.workQueue.**poll**();
..}

3. Then, the third is using simple try catch inside the call method but you can not catch the exception outside here.

4. The workaround is calling all the call methods from a call method of a TaskFactory, a factory that releases callables.