1、使用Timer

import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Timer;
import java.util.TimerTask;

public class TestTimer {
    public static void main(String[] args) {
        TimerTask timerTask = new TimerTask() {
            @Override
  public void run() {
                LocalDateTime current = LocalDateTime.now();
                String timeString = current.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
                System.out.println("task  run:"+ timeString);
            }
        };
        Timer timer = new Timer();
        //安排指定的任务在指定的时间开始进行重复的固定延迟执行。这里是每3秒执行一次
  timer.schedule(timerTask,3000,1000);
    }
}

2、ScheduledExecutorService

import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class TestScheduledExecutorService {

    public static void main(String[] args) {
        LocalDateTime current = LocalDateTime.now();
        String  timeString = current.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
        ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
        // 参数：1、任务体 2、首次执行的延时时间
        //      3、任务执行间隔 4、间隔时间单位
        service.scheduleAtFixedRate(()->System.out.println("task ScheduledExecutorService "+ timeString), 3, 1, TimeUnit.SECONDS);
    }
}

3、使用Spring Task

在启动类上使用@EnableScheduling注解开启对定时任务的支持，然后启动项目

@Slf4j
@Component
public class ScheduledService {
    @Scheduled(cron = "0/5 * * * * *")
    public void scheduled(){
        log.info("=====>>>>>使用cron  {}",System.currentTimeMillis());
    }
    @Scheduled(fixedRate = 5000)
    public void scheduled1() {
        log.info("=====>>>>>使用fixedRate{}", System.currentTimeMillis());
    }
    @Scheduled(fixedDelay = 5000)
    public void scheduled2() {
        log.info("=====>>>>>fixedDelay{}",System.currentTimeMillis());
    }
}

多线程

@Configuration
@EnableAsync
public class AsyncConfig {
     /*
    此处成员变量应该使用@Value从配置中读取
     */
    private int corePoolSize = 10;
    private int maxPoolSize = 200;
    private int queueCapacity = 10;
    @Bean
    public Executor taskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(corePoolSize);
        executor.setMaxPoolSize(maxPoolSize);
        executor.setQueueCapacity(queueCapacity);
        executor.initialize();
        return executor;
    }
}

@Configuration：表明该类是一个配置类 
@EnableAsync：开启异步事件的支持