Java实现定时器的四种方式

public class TimerExample {

    public static void main(String[] args) {
        // 创建定时器
        Timer timer = new Timer();
        // 创建定时器任务
        TimerTask task = new TimerTask() {
            @Override
            public void run() {
                System.out.println("Hello world!");
            }
        };

        timer.schedule(task, 1000); // 1秒后执行一次
        timer.schedule(task, 2000, 2000); // 两秒后每两秒执行一次
        timer.scheduleAtFixedRate(task, 3000, 3000); // 3秒后每3秒执行一次
        timer.scheduleAtFixedRate(task, new Date(), 4000); // 每4秒执行一次
    }

}

public class TimerExample {
    public static void main(String[] args) {
        // 创建定时器任务
        TimerTask timerTask = new TimerTask() {
            @Override
            public void run() {
                System.out.println("Hello world!");
            }
        };

        ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(2);

        scheduledThreadPool.schedule(timerTask, 1000, TimeUnit.MILLISECONDS);
        scheduledThreadPool.scheduleAtFixedRate(timerTask, 1000, 1000, TimeUnit.MILLISECONDS);
    }

}

@EnableScheduling
@SpringBootApplication
public class SpringbootApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootApplication.class, args);
    }

}

@Component
public class TimerTask {

    @Scheduled(cron = "0 7 2 26 7 *")
    public void task() {
        System.out.println("定时任务...");
    }

}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-quartz</artifactId>
</dependency>

public class QuartzJob implements Job {

    @Override
    public void execute(JobExecutionContext jobExecutionContext) {
        // 输出当前时间
        System.out.println(LocalDateTime.now());
    }

}

@Configuration
public class QuartzConfig {

    @Bean
    public JobDetail jobDetail() {
        return JobBuilder.newJob(QuartzJob.class)   // 绑定要运行的任务类的类对象
                .withIdentity("job")                // 设置job的名称
                .storeDurably()                     // 信息持久
                // 设置storeDurably之后,当没有触发器指向这个JobDetail时,JobDetail也不会从
                // Spring容器中删除,如果不设置这行,就会自动从Spring容器中删除
                .build();
    }

    @Bean
    public Trigger trigger() {
        // 定义Cron表达式，每10秒触发一次
        CronScheduleBuilder cronScheduleBuilder = 
                CronScheduleBuilder.cronSchedule("0/10 * * * * ?");
        
        return TriggerBuilder.newTrigger()
                .forJob(jobDetail())                 // 绑定JobDetail对象
                .withIdentity("trigger")             // 定义触发器名称
                .withSchedule(cronScheduleBuilder)   // 绑定Cron表达式
                .build();
    }

}