Multithreading: invokeAny returns the first result and cancels the rest

invokeAny submits every task but only waits for one of them to succeed, returning that single value and cancelling the tasks that are still running. It is useful when several strategies can answer the same question and only the quickest one matters.

Code

ExecutorService pool = Executors.newFixedThreadPool(2);
List<Callable<String>> tasks = List.of(
    () -> { Thread.sleep(60); return "slow"; },
    () -> "fast"
);
String winner = pool.invokeAny(tasks);
pool.shutdown();
System.out.println("Winner: " + winner);

Output

Winner: fast