线程池ExecutorService中submit和execute方法的区别

引言

     ExecutorService线程池执行线程时有submit 和execute 两种方法，它们两者之间有什么区别了？可能平时我们只是运用，没有深究其区别，在此我们可以看看它们的区别？

   1：executorService.execute()   

 1 public void execute(){
 2         ExecutorService executorService = Executors.newSingleThreadExecutor();
 3         executorService.execute(()->{
 4             try { 6                     Book book = new Book().setId("test" + (i + 1)).setName("平凡的世界").setAuthor("路遥").setContent("孙少安和田晓霞");
 7                     System.out.println("===book: " + JSONObject.toJSONString(book)); 9                 }
10             } catch (Exception e) {
11                 e.printStackTrace();
12             }
13         });
14         executorService.shutdown();
15     }

   无返回值，直接执行，因此不能阻塞线程，并且在执行异常时会抛出异常

 

 

 2：executorService.submit()方法

      有三种类型，返回future。    可以看ExecutorService接口的源码，submit有三种调用方式，Callable回调、result结果、Runnable

public interface ExecutorService extends Executor {
    
    <T> Future<T> submit(Callable<T> task);
    
    <T> Future<T> submit(Runnable task, T result);
    
    Future<?> submit(Runnable task);
    
}

      2.1： 带Callable回调函数的返回

 1 public void submit1() throws ExecutionException, InterruptedException {
 2         Callable<String> callable  = new Callable<String>() {
 3             @Override
 4             public String call() throws Exception {
 5                 return Thread.currentThread().getName()+"==== hello Callable";
 6             }
 7         };
 8         ExecutorService executorService = Executors.newSingleThreadExecutor();
 9         Future<String> future = executorService.submit(callable);
10         String s = executorService.submit(callable).get();
11         System.err.println(s);
12         System.out.println("======执行结果======"+future.get());
13         executorService.shutdown();
14     }

   返回结果：  

  

 

   2.2： 带T result) 返回结果的

 1 public void submit2() throws ExecutionException, InterruptedException {
 2         ExecutorService executorService = Executors.newSingleThreadExecutor();
 3         Future<?> future = executorService.submit(() -> {
 4             try {
 5                     Book book = new Book().setId("test").setName("平凡的世界").setAuthor("路遥").setContent("孙少安和田晓霞");
 6                     System.out.println("===book: " + JSONObject.toJSONString(book));
 7             } catch (Exception e) {
 8                 e.printStackTrace();
 9             }
10         },"返回结果了！");
11         executorService.shutdown();
12         Object o = future.get();
13         System.out.println("=====执行结果======"+o);
14         System.out.println("=====isDone======"+future.isDone());
15         System.out.println("=====cancel======"+future.cancel(true));
16         System.out.println("=====isCancelled======"+future.isCancelled());
17     }

   返回结果：  

 

  2.3：(Runnable task);  //不带返回结果

 1 public void submit3() throws ExecutionException, InterruptedException {
 2         ExecutorService executorService = Executors.newSingleThreadExecutor();
 3         Future<?> future = executorService.submit(() -> {
 4             try {
 5                     Book book = new Book().setId("test").setName("平凡的世界").setAuthor("路遥").setContent("孙少安和田晓霞");
 6                     System.out.println("===book: " + JSONObject.toJSONString(book));
 7             } catch (Exception e) {
 8                 e.printStackTrace();
 9             }
10         });
11         executorService.shutdown();
12         Object o = future.get();
13         System.out.println("=====执行结果======"+o);
14         System.out.println("=====isDone======"+future.isDone());
15         System.out.println("=====cancel======"+future.cancel(true));
16         System.out.println("=====isCancelled======"+future.isCancelled());
17     }

     返回结果：  

总结：

ExecutorService 的submit和execute的区别？
1: 接受的参数（任务类型）不一样。 execute只能接受Runnable类型的任务,submit不管是Runnable还是Callable类型的任务都可以接受，但是Runnable返回值均为void，所以使用Future的get()获得的还是null
2：返回值。execute没有返回值，submit有返回值，所以需要返回值的时候必须使用submit
3：异常的处理不同。
execute无返回值，直接执行，因此不能阻塞线程，并且在执行异常时会抛出异常
submit 有三种类型，返回future，可以阻塞获取线程执行结果，在执行异常时会被异常处理吃掉，不会抛出异常