本文主要是介绍Java并发系列 ScheduledExecutorService 使用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
本文介绍 ScheduledExecutorService 在Java1.5以后才出现的定时任务的，在Java5之后，并发线程这块发生了根本的变化，最重要的莫过于新的启动、调度、管理线程的一大堆API了。定时任务在1.5之前是使用 Timer 来实现的，但由于 Timer 有一些问题：
Timer对调度的支持是基于绝对时间,而不是相对时间的，
由此任务对系统时钟的改变是敏感的;ScheduledThreadExecutor只支持相对时间。
Timer的另一个问题在于，如果TimerTask抛出未检查的异常，Timer将会产生无法预料的行为。
Timer线程并不捕获异常，所以TimerTask抛出的未检查的异常会终止timer线程。
这种情况下，Timer也不会再重新恢复线程的执行了;它错误的认为整个Timer都被取消了。
此时，已经被安排但尚未执行的TimerTask永远不会再执行了，新的任务也不能被调度了。
所以建议使用1.5以后的 ScheduledExecutorService 这个定时服务对象
废话不说直接看代码吧：里面有相应的注释
package task;import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;/**官方文档：http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ScheduledExecutorService.html中文版：http://www.apihome.cn/api/java/ScheduledExecutorService.html*/
public class TaskTest {/*** 线程池的管理工具* 调度型线程池*/private final static ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);/*** 官方案例*/public static void beepForAnHour() {final Runnable beeper = new Runnable() {public void run() {System.out.println("beep");}};final ScheduledFuture<?> beeperHandle = scheduler.scheduleAtFixedRate(beeper, 10, 100, TimeUnit.MILLISECONDS);scheduler.schedule(new Runnable() {public void run() {System.out.println("cancel");/*** Attempts to cancel execution of this task. This attempt will fail if the task has already completed,* has already been cancelled, or could not be cancelled for some other reason.* If successful, and this task has not started when cancel is called, this task should never run. If the task has already started, * then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.* After this method returns, subsequent calls to isDone() will always return true. Subsequent calls to isCancelled() will always return true if this method returned true.* 试图取消执行这一任务。这种尝试会失败如果任务已经完成,已经被取消了,或者由于其他原因不能被取消。* 如果成功的话,这个任务并没有开始时取消,这个任务不应该运行。如果任务已经开始,那么mayInterruptIfRunning参数决定是否应该中断线程执行这个任务,试图阻止这项任务。* 该方法返回后,后续调用结束()将始终返回true。后续调用isCancelled()将始终返回true,如果这个方法返回true。*/beeperHandle.cancel(true);/*** 如果这个任务被取消之前完成正常。* Returns true if this task was cancelled before it completed normally.*/System.out.println(beeperHandle.isCancelled());}}, 60*60, TimeUnit.MILLISECONDS);}/*** Creates and executes a periodic action that becomes enabled first after the given initial delay, * and subsequently with the given period; that is executions will commence after initialDelay then initialDelay+period, * then initialDelay + 2 * period, and so on. If any execution of the task encounters an exception, * subsequent executions are suppressed. Otherwise, the task will only terminate via cancellation or termination of the executor. * If any execution of this task takes longer than its period, then subsequent executions may start late, but will not concurrently execute.* 创建并执行一个周期性的动作成为了第一个在给定的初始延迟之后,随后用给定的时期,这是执行后将开始initialDelay然后initialDelay +,然后initialDelay + 2 *时期,等等。* 如果任何执行任务遇到异常,后续执行的镇压。否则,只会终止的任务通过取消或终止执行器。如果执行这个任务花费的时间比其期,然后后续执行可能会迟到,但不会同时执行。* command：执行线程* initialDelay：初始化延时 启动以后多久执行* period：两次开始执行最小间隔时间 距离上次执行的时间* unit：计时单位*/public static void scheduleAtFixedRate(){scheduler.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {System.out.println("scheduleAtFixedRate"+System.currentTimeMillis());}}, 1000, 100, TimeUnit.MILLISECONDS);}public static void main(String[] args) {try {
// beepForAnHour();
// scheduleAtFixedRate();scheduleWithFixedDelay();
// lanuchTimer();
// Thread.sleep(3000);
// taskT();
// Thread.sleep(1000 * 60);
// studow();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}/*** Creates and executes a periodic action that becomes enabled first after the given initial delay,* and subsequently with the given delay between the termination of one execution and the commencement of the next. * If any execution of the task encounters an exception, subsequent executions are suppressed. Otherwise, * the task will only terminate via cancellation or termination of the executor.* 创建并执行一个周期性的动作成为了第一个在给定的初始延迟之后,随后用给定的延迟之间的终止执行和接下来的毕业典礼。如果任何执行任务遇到异常,后续执行的镇压。* 否则,只会终止的任务通过取消或终止执行器。*/public static void scheduleWithFixedDelay() {scheduler.scheduleWithFixedDelay(new Runnable() {public void run() {System.out.println("scheduleWithFixedDelay---->"+System.currentTimeMillis());}}, 1000, 100, TimeUnit.MILLISECONDS);}/*** 关闭执行服务对象*/public static void studow() {scheduler.shutdown();}/*** 凌晨3点钟执行*/public static void taskTimr() {long oneDay = 24 * 60 * 60 * 1000; long initDelay = getTimeMillis("20:00:00") - System.currentTimeMillis(); initDelay = initDelay > 0 ? initDelay : oneDay + initDelay; scheduler.scheduleAtFixedRate( new EchoServer(), initDelay, oneDay, TimeUnit.MILLISECONDS); }/** * 获取指定时间对应的毫秒数 * @param time "HH:mm:ss" * @return */ private static long getTimeMillis(String time) { try { DateFormat dateFormat = new SimpleDateFormat("yy-MM-dd HH:mm:ss"); DateFormat dayFormat = new SimpleDateFormat("yy-MM-dd"); Date curDate = dateFormat.parse(dayFormat.format(new Date()) + " " + time); return curDate.getTime(); } catch (Exception e) { e.printStackTrace(); } return 0; } }class EchoServer implements Runnable { @Override public void run() { try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("This is a echo server. The current time is " + System.currentTimeMillis() + "."); }
}
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