Future#cancel()を使ってみた

public class CancelTest {
  public static void main(String[] args) 
    throws InterruptedException, ExecutionException {
    ExecutorService service = Executors.newFixedThreadPool(2);
    Future<String> future1 = service.submit(new WaitThread("1"));
    Future<String> future2 = service.submit(new WaitThread("2"));
    Future<String> future3 = service.submit(new WaitThread("3"));
    Future<String> future4 = service.submit(new WaitThread("4"));
        
    future4.cancel(false);
        
    System.out.println(future1.get());
    System.out.println(future2.get());
    System.out.println(future3.get());
    System.out.println(future4.get());
  }
}

class WaitThread implements Callable<String> {
  private String id = null;
  public WaitThread(String id) {
    this.id = id;
  }
  public String call() throws Exception {
    System.out.println("invoked:"+this.id);
    String rtn = "result";
    TimeUnit.SECONDS.sleep(6);
    return rtn + ":" + this.id;
  }
}