java Future interface

java.util.concurrent.Future<V>
V - The result type returned by this Future's get method
Future 비동기 연산의 결과를 나타냄

Example

import java.util.concurrent.*;

public class FutureIsDoneExample {
  public static void main(String[] args) throws InterruptedException, ExecutionException {
    ExecutorService executorService = Executors.newSingleThreadExecutor();

    Future<String> future = executorService.submit(() -> {
      Thread.sleep(2000);
      return "Hello from Callable";
    });

    while(!future.isDone()) {
      System.out.println("Task is still not done...");
      Thread.sleep(200);
    }

    System.out.println("Task completed! Retrieving the result");
    String result = future.get();
    System.out.println(result);

    executorService.shutdown();
  }
}

code from: https://www.callicoder.com/java-callable-and-future-tutorial/