通过代码示例了解submit与execute的区别

(1)可以接受的任务类型

submit:

通过代码示例了解submit与execute的区别

execute:

通过代码示例了解submit与execute的区别

可以看出:

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

由Callable和Runnable的区别可知:

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

1.execute中抛出异常

execute中的是Runnable接口的实现,所以只能使用try、catch来捕获CheckedException,通过实现UncaughtExceptionHande接口处理UncheckedException

即和普通线程的处理方式完全一致

2.submit中抛出异常

不管提交的是Runnable还是Callable类型的任务,如果不对返回值Future调用get()方法,都会吃掉异常

先来看下Callable定义

public interface Callable<V> {
V call() throws Exception;
}

其中的call能够抛出Exception异常,所以不管是CheckedException还是UncheckedException,直接抛出即可

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
 
public class ThreadExceptionTest {
  public static void main(String[] args) {
    ExecutorService executor = Executors.newCachedThreadPool();
    
    Future<Boolean> future = executor.submit(new CallableTask());
    try {
      future.get();
    } catch (InterruptedException e) {
      e.printStackTrace();
    } catch (ExecutionException e) {
      e.printStackTrace();
    }
    
    executor.shutdown();//必须不能忘,否则会一致卡在那里
  }
}
 
class CallableTask implements Callable<Boolean>{
  public Boolean call() throws Exception {
//    InputStream in = new FileInputStream(new File("xx.pdf"));
    int num = 3/0;
    return false;
  }
  
}

结果为:

java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
  at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
  at java.util.concurrent.FutureTask.get(FutureTask.java:83)
  at my.ThreadExceptionTest.main(ThreadExceptionTest.java:21)
Caused by: java.lang.ArithmeticException: / by zero
  at my.CallableTask.call(ThreadExceptionTest.java:57)
  at my.CallableTask.call(ThreadExceptionTest.java:1)
  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
  at java.util.concurrent.FutureTask.run(FutureTask.java:138)
  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
  at java.lang.Thread.run(Thread.java:619)

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通过代码示例了解submit与execute的区别

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