定时任务--单点系统

public class Demo01 {
    static long count = 0;
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(1000);
                        count++;
                        System.out.println(count);
                    } catch (Exception e) {
                        // TODO: handle exception
                    }
                }
            }
        };
        Thread thread = new Thread(runnable);
        thread.start();
    }
}

/**
 * 使用TimerTask类实现定时任务
*/
public class Demo02 {
    static long count = 0;

    public static void main(String[] args) {
        TimerTask timerTask = new TimerTask() {

            @Override
            public void run() {
                count++;
                System.out.println(count);
            }
        };
        Timer timer = new Timer();
        // 天数
        long delay = 0;
        // 秒数
        long period = 1000;
        timer.scheduleAtFixedRate(timerTask, delay, period);
    }

}

public class Demo003 {
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            public void run() {
                // task to run goes here
                System.out.println("Hello !!");
            }
        };
        ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
        // 第二个参数为首次执行的延时时间，第三个参数为定时执行的间隔时间
        service.scheduleAtFixedRate(runnable, 1, 1, TimeUnit.SECONDS);
    }
}

 Quartz定时任务

1、引入jar包

<dependencies>
        <!-- quartz -->
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz</artifactId>
            <version>2.2.1</version>
        </dependency>
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz-jobs</artifactId>
            <version>2.2.1</version>
        </dependency>
    </dependencies>

public class MyJob implements Job {
    public void execute(JobExecutionContext context) throws JobExecutionException {
        System.out.println("quartz MyJob date:" + new Date().getTime());
    }
}

 //1.创建Scheduler的工厂
      SchedulerFactory sf = new StdSchedulerFactory();
      //2.从工厂中获取调度器实例
      Scheduler scheduler = sf.getScheduler();


      //3.创建JobDetail
      JobDetail jb = JobBuilder.newJob(MyJob.class)
              .withDescription("this is a ram job") //job的描述
              .withIdentity("ramJob", "ramGroup") //job 的name和group
              .build();

      //任务运行的时间，SimpleSchedle类型触发器有效
      long time=  System.currentTimeMillis() + 3*1000L; //3秒后启动任务
      Date statTime = new Date(time);

      //4.创建Trigger
          //使用SimpleScheduleBuilder或者CronScheduleBuilder
      Trigger t = TriggerBuilder.newTrigger()
                  .withDescription("")
                  .withIdentity("ramTrigger", "ramTriggerGroup")
                  //.withSchedule(SimpleScheduleBuilder.simpleSchedule())
                  .startAt(statTime)  //默认当前时间启动
                  .withSchedule(CronScheduleBuilder.cronSchedule("0/2 * * * * ?")) //两秒执行一次
                  .build();

      //5.注册任务和定时器
      scheduler.scheduleJob(jb, t);

      //6.启动 调度器
      scheduler.start();

cron表达示：http://cron.qqe2.com/