在完成任何先前的异步方法之后，在Java中执行方法？

Question

I'm trying to use Completetable future to run two task in async. The program runs asynchronously, such that a() and b() run first, in any order, concurrently. But c() can only run after either one of a() or b() completes

class Pair{
  public void pair2() throws InterruptedException, ExecutionException {
    CompletableFuture<Void> fa = CompletableFuture.runAsync(() -> a());
    CompletableFuture<Void> fb = CompletableFuture.runAsync(() -> b());

    if(fa.isDone || fb.isDone){ //should not be if loop.
      c();
    }
    return;
  }

  public void a(){
    System.out.println("I'm a.");
    return;
  }
  public void b(){
    System.out.println("I'm b.");
    return; 
  }

  public void c(){
    System.out.println("I'm c, I cannot be the first!");
    return;
  }
}

I'm not familiar with the CompletableFuture API, is there a way to check if either of the task is done and call upon the next method C?

Answer 1

You could use one of the xxxEither methods. For example:

CompletableFuture<Void> fc = fa.acceptEither(fb, v -> c());

Or you could use the anyOf method:

CompletableFuture.anyOf(fa, fb).thenRun(this::c);