Java 线程池 ScheduledThreadPool的使用及示例代码

1、ScheduledThreadPool简介

ScheduledThreadPool是核心线程数量固定，非核心线程数量无限，执行完闲置 10ms 后回收，任务队列为延时阻塞队列。一般是用在执行定时或周期性任务的使用场景。相对于通过使用 ThreadPoolExecutor 的方式，使用ScheduledThreadPool更方便，有些参数可能不需要设置，可以根据实现情况使用。

2、newFixedThreadPool源码

private static final long DEFAULT_KEEPALIVE_MILLIS = 10L; public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {    return new ScheduledThreadPoolExecutor(corePoolSize);}public ScheduledThreadPoolExecutor(int corePoolSize) {    super(corePoolSize, Integer.MAX_VALUE,          DEFAULT_KEEPALIVE_MILLIS, MILLISECONDS,          new DelayedWorkQueue());} public static ScheduledExecutorService newScheduledThreadPool(        int corePoolSize, ThreadFactory threadFactory) {    return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);}public ScheduledThreadPoolExecutor(int corePoolSize,                                   ThreadFactory threadFactory) {    super(corePoolSize, Integer.MAX_VALUE,          DEFAULT_KEEPALIVE_MILLIS, MILLISECONDS,          new DelayedWorkQueue(), threadFactory);}

3、使用示例

import java.util.concurrent.*;import java.util.Date; import java.text.DateFormat;import java.text.SimpleDateFormat;public class Main {  public static void main(String[] args) throws Exception {            ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);    // 需执行的任务    Runnable task =new Runnable(){      public void run() {              Date date=new Date();              DateFormat dateFormat=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");              System.out.println(" 当前时间为："+dateFormat.format(date));      }    };    //添加任务    scheduledThreadPool.schedule(task, 1, TimeUnit.SECONDS); // 延迟1s后执行任务    scheduledThreadPool.scheduleAtFixedRate(task,10,1000,TimeUnit.MILLISECONDS);// 延迟10ms后、每隔1000ms执行任务    scheduledThreadPool.awaitTermination(10000, TimeUnit.MILLISECONDS);    System.exit(0); //success  }}