ExecutorService的execute和submit方法

/*这个是今天question 1的两个例子*/

/*题目；The first example uses a threads to execute 4 instances of the

* Runnable interface T1.Task T1 is implemented as an implementation of the Runnable

* interface and the code is contained in the run method .In this simple example the task

* is to print a number 10 times on the screen followed by a newline. The array of class

* Future is used to hold references to each task submitted to the pool of thread.In this

* case 4 jobs are going to be submitted and ,hence,the array has size 4.Once the jobs

* are submitted we want main() to wait for all the tasks in the threadpool to complete.

* This is done by invoking get on each job submitted.Then the pool is shut down. */

import java.util.concurrent.*;

class ThreadPool1 {

public static void main(String arg[]){

ExecutorService pool;

pool=Executors.newFixedThreadPool(2);

Runnable r;

Future f[]=new Future[4];

for(int j=0;j<4;j++){

r=new T1(j);

f[j]=pool.submit(r);

}

/*下面一段代码是question1的下半截用到的*/

try{

for(Future x: f)x.get();

}

catch(InterruptedException e){}

catch(ExecutionException e){}

pool.shutdown();

System.out.println("Main finished");

}

}

class T1 implements Runnable{

int k;

public T1(int kk){

k=kk;

}

public void run(){

for(int j=0;j<10;j++);

System.out.println();

}

}

===================================解决方案========================================================

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

public class ExecutorServiceTest {

/*

* 因为之前一直用的execute方法,最近有个情况需要 用到submit方法,

*/

/*

* 接收的参数不一样 submit有返回值,而execute没有

*

* Method submit extends base method Executor. execute by creating and

* returning a Future that can be used to cancel execution and/or wait for

* completion.

*

* 用到返回值的例子,比如说我有很多个做validation的task,我希望所有的task执行完,

* 然后每个task告诉我它的执行结果,是成功还是失败,如果是失败. 原因是什么： 然后我就可以把所有失败的原因综合起来发给调用者。

*

*

* 个人觉得cancel executio这个用处不大,很少有需要去取消执行的。

*

* 3,submit方便Exception处理 意思就是如果你在你的task里会抛出checked或者unchecked

* exception，而你又希望 外面的调用者能够感知这些exception并做出及时的处理，那么就需要用到submit，通过

* 捕获Future.get抛出的异常。

*

*

*/

public static void main(String[] args) {

ExecutorService executorService = Executors.newCachedThreadPool();

List<Future<String>> resultList = new ArrayList<Future<String>>();

// 创建10个任务并执行

for (int i = 0; i < 4; i++) {

// 使用ExecutorService执行Callable类型的任务,并将结果保存在future变量中

Future<String> future = (Future<String>) executorService

.submit(new Task(i));

// 将任务执行结果存储到List中

resultList.add(future);

}

// 1、shutdown方法：这个方法会平滑地关闭ExecutorService，当我们调用这个方法时，

// ExecutorService停止接受任何新的任务且等待已经提交的任务执行完成(已经提交的任

// 务会分两类：一类是已经在执行的，另一类是还没有开始执行的)，当所有已经

// 提交的任务执行完毕后将会关闭ExecutorService。这里我们先不举例在下面举例

// 遍历任务的结果

for (Future<String> fs : resultList) {

try {

// 打印各个线程(任务)执行的结果

System.out.println(fs.get());

} catch (InterruptedException e) {

e.printStackTrace();

} catch (ExecutionException e) {

e.printStackTrace();

return;

}

}

executorService.shutdown();

}

}

class Task implements Runnable {

private int id;

public Task(int id) {

this.id = id;

}

/*

* 任务的具体过程,一旦任务传递ExecutorService 的 submit方法,

* 则该方法自动在一个线程上执行。

*/

public void run() {

System.out.println("run()方法被自动调用,干活!!!"+Thread.currentThread().getName());

for (int i = 0; i < 10; i++) {

System.out.println(

""+id+" "+Thread.currentThread().getName()

);

}

}

}