One of the improvements in Java 9 CompletableFuture is the orTimeout method:

CompletableFuture orTimeout(long timeout, TimeUnit unit)

If not completed before specified timeout, completes CompletableFuture exceptionally with TimeoutException.

Let’s say in the following example, we need the task to be completed in 3 seconds, but the task lasts 6 seconds: 

public static void main(String[] args) throws ExecutionException, InterruptedException {
  int timeout = 3;
  runTask()
      .orTimeout(timeout, TimeUnit.SECONDS)
      .whenComplete((result, exception) -> {
        if (exception == null) {
          System.out.println("result: " + result);
        } else {
          System.out.println("Task is not finished in " + timeout
              + " seconds... Completing with TimeoutException");
        }
      });
}

[addToAppearHere]
private static CompletableFuture runTask() {
  return CompletableFuture.supplyAsync(() -> {
    for (int i = 1; i < 6; i++) {
      try {
        Thread.sleep(1000);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      System.out.println("running task - " + i + " seconds");
    }
    return "completed";
  });
}

//output

running task - 1 seconds
running task - 2 seconds
Task is not finished in 3 seconds... Completing with TimeoutException
Exception in thread "main" java.util.concurrent.ExecutionException: java.util.concurrent.TimeoutException