scheduleAtFixedRate 没有什么歧义，很容易理解，就是每隔多少时间，固定执行任务。

scheduleWithFixedDelay 比较容易有歧义

貌似也是推迟一段时间执行任务，但Oracle的解释如下,delay 的意思是当结束前一个执行后延迟的时间

scheduleWithFixedDelay Parameters:

command - the task to execute

initialDelay - the time to delay first execution

delay - the delay between the termination of one execution and the commencement of the next

unit - the time unit of the initialDelay and delay parameters

scheduleWithFixedDelay 比如当前一个任务结束的时刻，开始结算间隔时间，如0秒开始执行第一次任务，任务耗时5秒，任务间隔时间3秒，那么第二次任务执行的时间是在第8秒开始。

 

import java.util.Date; public class WorkerThread implements Runnable{ private String command;         public WorkerThread(String s){        this.command=s;    }     @Override    public void run() {        System.out.println(Thread.currentThread().getName()+" Start. Time = "+new Date());        processCommand();        System.out.println(Thread.currentThread().getName()+" End. Time = "+new Date());    }     private void processCommand() {        try {            Thread.sleep(5000);        } catch (InterruptedException e) {            e.printStackTrace();        }    }     @Override    public String toString(){        return this.command;    }}

 

 

import java.util.Date;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;  public class ScheduledThreadPool {     public static void main(String[] args) throws InterruptedException {        ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5);        System.out.println("Current Time = "+new Date());        for(int i=0; i<10; i++){            Thread.sleep(1000);            WorkerThread worker = new WorkerThread("do heavy processing");            //scheduledThreadPool.schedule(worker, 3, TimeUnit.SECONDS);            //scheduledThreadPool.scheduleAtFixedRate(worker, 5, 5, TimeUnit.SECONDS);            scheduledThreadPool.scheduleWithFixedDelay(worker, 5, 3, TimeUnit.SECONDS);        }        Thread.sleep(300000);                 scheduledThreadPool.shutdown();        while(!scheduledThreadPool.isTerminated()){        }        System.out.println("Finished all threads");    } }