Java: Async method invocation which returns different type data

Question

I want to execute 3 java methods and all of them return different type of data (say Class type). Is there a way I can run these 3 methods in parallel using ExecutorService ? In this way call() method needs to return something in specific which spoils my idea of using it.

Let me know if there is a way to achieve this.

Answer 1

The call() method usually returns something specific, that's why it's useful. You can create 3 different types of Callables and there's no problem.

Callable<A> c1 = () -> { return getA(); };
Callable<B> c2 = () -> { return getB(); };
Callable<C> c3 = () -> { return getC(); };

Future<A> f1 = executor.submit(c1);
Future<B> f2 = executor.submit(c2);
Future<C> f3 = executor.submit(c3);

Answer 2

Executors accept Callable tasks, which are generic functional interfaces designed to return arbitrary types.

    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.submit(() -> "Hello");
    executorService.submit(() -> new BigDecimal("1.1"));
    executorService.submit(() -> new ArrayList());

submit() returns a Future, a generic holder for the computation result, which will have the same generic type as the data returned by your Callable.

    Future<String> future = executorService.submit(() -> "Hello");

To access the result, simply call get() :

    String result = future.get();