Question

How can I get output from Java anonymous classes? In .Net I would use closures.

executor = Executors.newSingleThreadExecutor();
final Runnable runnable = new Runnable() {
  public Exception exception;

  @Override
  public void run() {
    try {
      doSomething();
    }
    catch (Exception exception) {
      // I'd like to report this exception, but how?
      // the exception member is not readable from outside the class (without reflection...)
      this.exception = exception;
    }
  }
};

executor.submit(runnable);

// Here I'd like to check if there was an exception

Answer 1

The Executor interface offers no way to do this. However, when you call newSingleThreadExecutor() you will get an ExecutorService which contains functionality for that.

Calling ExecutorService.submit() returns an instance of Future<?>, which you can use to get the result value of the computation.

If the execution resulted in an exception, calling get will cause an ExecutionException to be thrown.