What are Java Futures and how do they work?

What are Java Futures and how do they work?

Java Futures are part of the java.util.concurrent package, allowing you to represent the result of an asynchronous computation.

Can you give me an example of how to use a Future in Java?

Sure! You can use the ExecutorService to submit a Callable task and get a Future object. Here's a simple example:

ExecutorService executor = Executors.newFixedThreadPool(1);
Future<Integer> future = executor.submit(() -> {
    // Simulate a long-running task
    Thread.sleep(1000);
    return 42;
});

// Do other work...

try {
    Integer result = future.get(); // This will block until the result is available
    System.out.println("Result: " + result);
} catch (InterruptedException | ExecutionException e) {
    e.printStackTrace();
} finally {
    executor.shutdown();
}

What happens if I call get() on a Future before the task is complete?

If you call get() on a Future before the task is complete, it will block the current thread until the result is available or an exception is thrown.

Are there any alternatives to using Futures in Java?

Yes, alternatives include using CompletableFuture for more complex asynchronous programming or reactive programming libraries like RxJava.