[Java] How to execute tasks on a regular basis

Introduction

This time, I will explain how to execute tasks regularly in Java. This function is often used in batch processing.

In the sample, we will use the Timer class to implement the process of executing tasks on a regular basis.

Then I will explain it immediately.

1. Development environment

After that, it will be explained in the following versions and environments.

IDE：eclipse Java version: 8

2. Folder structure

The folder structure of this sample program is as follows.

3. Implementation of sample program

3-1. Implementation of tasks that you want to execute on a regular basis

Implement tasks that you want to execute on a regular basis using the TimerTask class. This time, we will implement a sample process that periodically outputs "The task has been executed" to the console.

Main.java

package main;
//The part to be added this time
import java.util.TimerTask;

public class Main {
    public static void main(String[] args) {
        //The part to be added this time
        TimerTask task = new TimerTask() {
            public void run() {
                //Processing that you want to execute on a regular basis
                System.out.println("The task has been executed.");
            }
        };
    }
}

Also, in order to check how many times it has been executed, let's implement it so that you can see the number of times as follows.

Main.java

package main;

import java.util.TimerTask;

public class Main {
    public static void main(String[] args) {

        TimerTask task = new TimerTask() {
            int count = 0; //Processing to be added this time
            public void run() {
                //Processing that you want to execute on a regular basis
                count++; //Processing to be added this time
                System.out.println(count + "The second task has been performed."); //Processing to be corrected this time
            }
        };
    }
}

3-2. Implementation of schedule

Next, we will implement when to start executing the task and how often to execute the task.

As for the implementation method, use the scheduleAtFixedRate method of the Timer class. The usage is as follows.

Timer timer = new Timer();
timer.scheduleAtFixedRate(Tasks you want to perform on a regular basis,Time to execute the first task(ms),Interval between tasks to perform(ms));

Although it is the second argument of the scheduleAtFixedRate method, not only "time until the first task execution" but also "task start time" can be specified by Date type.

In this sample, we will implement the process that the task is executed at 3 second intervals 1 second after PGM is executed.

Main.java

package main;

import java.util.Timer; //Processing to be added this time
import java.util.TimerTask;

public class Main {
    public static void main(String[] args) {

        Timer timer = new Timer(); //Processing to be added this time
        TimerTask task = new TimerTask() {
            int count = 0;
            public void run() {
                //Processing that you want to execute on a regular basis
                count++;
                System.out.println(count + "The second task has been performed.");
            }
        };
        timer.scheduleAtFixedRate(task,1000,3000); //Processing to be added this time
    }
}

After completing the above implementation, right-click Main.java> Run Java Application to execute it.

It is OK if the following words are output to the console at 3 second intervals.

console

The first task has been performed.
The second task has been performed.
The third task has been performed.
The fourth task has been performed.
・ ・ ・

at the end

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