How many ways are there to implement a Java timer?

There are many ways to implement Java timers. Common ones include the Timer class, ScheduledExecutorService interface and Quartz framework.

1. Timer class
The Timer class is a timer tool class provided by Java, which can be used to perform some scheduled tasks. It can implement simple timer functions, but there are some problems in a multi-threaded environment.

Code example:

import java.util.Timer;
import java.util.TimerTask;

public class TimerExample {
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                // 定时任务的具体逻辑
                System.out.println("Task executed at: " + System.currentTimeMillis());
            }
        }, 1000); // 延迟1秒后执行
    }
}

2. ScheduledExecutorService interface
ScheduledExecutorService interface is an interface provided by Java for creating scheduled tasks. It is a sub-interface of ExecutorService and can be used after the specified delay. Or perform tasks on a regular basis.

Code example:

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

public class ScheduledExecutorServiceExample {
    public static void main(String[] args) {
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
        executor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                // 定时任务的具体逻辑
                System.out.println("Task executed at: " + System.currentTimeMillis());
            }
        }, 0, 1, TimeUnit.SECONDS); // 每隔1秒执行一次
    }
}

3. Quartz framework
Quartz is a powerful open source scheduled task scheduling framework that can realize the scheduling of complex scheduled tasks.

Code examples:

import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.impl.StdSchedulerFactory;
import org.quartz.JobBuilder;
import org.quartz.Trigger;
import org.quartz.TriggerBuilder;

public class QuartzExample {
    public static class MyJob implements Job {
        @Override
        public void execute(JobExecutionContext context) throws JobExecutionException {
            // 定时任务的具体逻辑
            System.out.println("Task executed at: " + System.currentTimeMillis());
        }
    }

    public static void main(String[] args) throws SchedulerException {
        Scheduler scheduler = StdSchedulerFactory.getDefaultScheduler();
        scheduler.start();

        JobDetail job = JobBuilder.newJob(MyJob.class).build();

        Trigger trigger = TriggerBuilder.newTrigger()
                .startNow()
                .withSchedule(SimpleScheduleBuilder.repeatSecondlyForever(1)) // 每隔1秒执行一次
                .build();

        scheduler.scheduleJob(job, trigger);
    }
}

The above are code examples of commonly used scheduled task implementation methods in Java. You can choose the appropriate implementation method according to specific needs.

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