分为四个步骤

1. 定义一个java.util.concurrent.ScheduledExecutorService scheduledService
2. scheduledService = java.util.concurrent.Executors.newScheduledThreadPool(1)
3. 定义 Runnable
4. scheduledService.scheduleAtFixedRate(Runnable, initDelay, period, TimeUnit unit)

示例代码

package com.yj.test.javaBases.testSchedule;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class ScheduleSayHello {
    
    private ScheduledExecutorService scheduledService;
    private Runnable runnable;
    public ScheduleSayHello(){
        scheduledService = Executors.newScheduledThreadPool(1);
        runnable = new Runnable(){

            @Override
            public void run() {
                System.out.println("helloworld");
            }
            
        };
    }
    public void test(){
        scheduledService.scheduleAtFixedRate(runnable, 5, 3, TimeUnit.SECONDS);
    }
    public static void main(String[] args) {
        new ScheduleSayHello().test();
    }
}