for (int i = 0; i < numThreads; i++) {
      Thread thread = new Thread(task);
      thread.setUncaughtExceptionHandler(
          new UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread t, Throwable e) {
              exceptions.add(e);
            }
          });
      threads.add(thread);
    }
    for (Thread t : threads) {
      t.start();
    }

    for (int i = 0; i < numThreads; i++) {
      Thread thread = new Thread(task);
      thread.setUncaughtExceptionHandler(
          new UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread t, Throwable e) {
              exceptions.add(e);
            }
          });
      threads.add(thread);
    }
    for (Thread t : threads) {
      t.start();
    }