java - 将 Future 与 ExecutorService 结合使用

Question

我需要并行执行两个任务并等待它们完成。我还需要第二个任务的结果，因为我正在使用 Future。

我的问题是，我需要 executor.awaitTermination 来加入任务，还是 Future.get() 会处理它。还有更好的方法可以使用 Java 8 实现此目的吗？

public class Test {

    public static void main(String[] args) {
        test();
        System.out.println("Exiting Main");
    }

    public static void test() {
        System.out.println("In Test");
        ExecutorService executor = Executors.newFixedThreadPool(2);

        executor.submit(() -> {
            for(int i = 0 ; i< 5 ; i++) {
                System.out.print("["+i+"]");
                try {
                    Thread.sleep(1000);
                } catch (Exception e) {e.printStackTrace();}
            }
        });

        Future<String> result = executor.submit(() -> {
            StringBuilder builder = new StringBuilder();
            for(int i = 0 ; i< 10 ; i++) {
                System.out.print("("+i+")");
                try {
                    Thread.sleep(1000);
                } catch (Exception e) {e.printStackTrace();}
                builder.append(i);
            }
            return builder.toString();
        });

        System.out.println("shutdown");
        executor.shutdown();
        // DO I need this code : START
        System.out.println("awaitTermination");
        try {
            executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
        } catch (InterruptedException e) {
            System.out.println("Error");
        }
        // DO I need this code : END
        System.out.println("Getting result");
        try {
            System.out.println(result.get());
        } 
        catch (InterruptedException e) {e.printStackTrace();} 
        catch (ExecutionException e) {e.printStackTrace();}
        System.out.println("Exiting Test");
    }

}

带有awaitTermination的输出:

In Test
[0]shutdown
(0)awaitTermination
[1](1)[2](2)[3](3)[4](4)(5)(6)(7)(8)(9)Getting result
0123456789
Exiting Test
Exiting Main

不带awaitTermination的输出:

In Test
[0]shutdown
Getting result
(0)[1](1)[2](2)[3](3)[4](4)(5)(6)(7)(8)(9)0123456789
Exiting Test
Exiting Main

Answer 1

从获取 javadoc:

Waits if necessary for the computation to complete, and then retrieves its result.

get 将仅等待第二个任务。

来自 awaitTermination javadoc:

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

awaitTermination 将等待所有任务。