Java并发编程之线程管理（Executor框架15）

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4.5指定一段时间运行并发任务

当你发送一个任务给指定的executor时，它依据executor的配置来迅速被运行。当你对线程的运行不太感兴趣，只需要它快速的运行就可以了，这就是它的使用场合。当你想间歇地执行一个任务或者定期地执行一个任务。对于这些目的，Executor框架提供了一个ScheduledThreadPoolExecutor类。请看下面实例实例代码。

定义Task类，实现一个简单的逻辑。

import java.util.Date;import java.util.concurrent.Callable;import java.util.concurrent.Executors;importjava.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;  /** * This class implements the task ofthis example. Writes a * message to the console with theactual date and returns the * 'Hello, world' string * */public class Task implements Callable<String> {     /**     * Name of the task     */    private Stringname;       /**     * Constructor of the class     * @param name Name of the task     */    public Task(String name) {        this.name=name;    }       /**     * Main method of the task. Writes a message tothe console with     * the actual date and returns the 'Helloworld' string     */    @Override    public String call()throws Exception {        System.out.printf("%s: Starting at : %s\n",name,new Date());        return"Hello, world";    }     /**     * Main method of the example     * @param args     */    public staticvoidmain(String[] args) {         // Create a ScheduledThreadPoolExecutor        ScheduledExecutorService executor=(ScheduledExecutorService)Executors.newScheduledThreadPool(1);               System.out.printf("Main: Starting at: %s\n",new Date());               // Send the tasks to the executor with the specified delay        for (int i=0; i<5; i++) {            Task task=new Task("Task "+i);            executor.schedule(task,i+1 ,TimeUnit.SECONDS);        }               // Finish the executor        executor.shutdown();               // Waits for the finalization of the executor        try {            executor.awaitTermination(1,TimeUnit.DAYS);        } catch (InterruptedException e) {            e.printStackTrace();        }         // Writes the finalization message        System.out.printf("Core: Ends at: %s\n",new Date());    }}

运行结果：

Main:Starting at: Sun Mar 30 23:03:12 CST 2014Task0: Starting at : Sun Mar 30 23:03:13 CST 2014Task1: Starting at : Sun Mar 30 23:03:14 CST 2014Task2: Starting at : Sun Mar 30 23:03:15 CST 2014Task3: Starting at : Sun Mar 30 23:03:16 CST 2014Task4: Starting at : Sun Mar 30 23:03:17 CST 2014Core:Ends at: Sun Mar 30 23:03:17 CST 2014

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