https://github.com/cleantutorials/JConsole/blob/master/src/main/java/com/cleantutorials/jconsole/cpu/CPUUsage.java

CPUUsage.java

package com.cleantutorials.jconsole.cpu;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Random;

/**
 * A class to demonstrate the CPU usage in the system space and the user space
 * as seen in JConsole. Note: Only to demonstrate an example, manually kill the
 * process if you want to run the example or it can eat up a lot of resources.
 */
public class CPUUsage {
	public static void main(String[] args) throws IOException, InterruptedException {
		GenerateRandomNumner generator = new GenerateRandomNumner();
		generator.setName("Random Generator");
		generator.start();
	}
}

/**
 * Thread that generates lots of random number and write it to a file.
 * Used in demonstrating the CPU time and User time in JConsole.
 */
class GenerateRandomNumner extends Thread {
	@Override
	public void run() {
		File file = new File("random_numbers.txt");
		Random rand = new Random();

		try (BufferedWriter br = new BufferedWriter(new FileWriter(file))) {
			for (int i = 0; i < 10000000; i++) {
				// Contributes to the time executing calls in user space.
				String randomNumer = Integer.toString(rand.nextInt());
				// Contributes to the time executing calls in kernel space.
				br.write(randomNumer + ",");
				// Flush the buffer.
				br.flush();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}