ScheduledThreadPoolExecutor多线程处理
1.作用
ScheduledThreadPoolExecutor用于定时任务，这里的定时意义在于：适用于多个后台线程执行周期性任务
2.ScheduledThreadPoolExecutor类
0.先看下ScheduledThreadPoolExecutor类，继承了ThreadPoolExecutor类，实现ScheduledExecutorService类
1.创建ScheduledThreadPoolExecutor的方法如下：
corePoolSize是线程池中的核心线程数，ThreadFactory是线程2.有以下几种方法
- schedule(Runnable command, long delay, TimeUnit unit) // 无返回值的延迟任务
- schedule(Callable callable, long delay, TimeUnit unit) // 有返回值的延迟任务
- scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) // 固定频率周期任务
- scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) // 固定延迟周期任务
3.代码例子
1. scheduleAtFixedRate
package com.demo;
import lombok.extern.slf4j.Slf4j;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/**
* @Author：xiaxia
* @Date：2021/7/27
*/
@Slf4j
public class ThreadTest {
public static void main(String[] args){
ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);
scheduledThreadPool.scheduleAtFixedRate(() -> {
try {
sleep(1000); // 睡眠 1s，
log.info("run task");
} catch (InterruptedException e) {
e.printStackTrace();
}
//log.info("run task");
}, 1, 2, TimeUnit.SECONDS);
}
private static void sleep(int i) throws InterruptedException {
Thread.sleep(1000);
}
}
输出如下：
2.schedule
public class ThreadTest {
public static void main(String[] args){
ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);
try {
//schedule to run after sometime
System.out.println("Current Time = "+getNowDate());
for(int i=0; i<3; i++){
Thread.sleep(1000);
WorkerThread worker = new WorkerThread();
//延迟5秒后执行
scheduledThreadPool.schedule(worker, 100, TimeUnit.SECONDS);
}
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
scheduledThreadPool.shutdown();
while(!scheduledThreadPool.isTerminated()){
//wait for all tasks to finish
}
System.out.println("Finished all threads");
}
/**
* 获取现在时间
*
* @return 返回时间类型 yyyy-MM-dd HH:mm:ss
*/
public static String getNowDate() {
Date currentTime = new Date();
SimpleDateFormat formatter;
formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String ctime = formatter.format(currentTime);
return ctime;
}
}
输出如下：
