example of non thread safe code

Main.java

import java.util.ArrayList;
import java.util.Arrays;

/**
 * @author Mehdi Maick
 */
public class Main {

    static int var = 0;

    static int ind = 0;

    public static void main(String[] args) throws InterruptedException {

        Thread t1 = new Thread(() -> {
            while (var < 1000) {
                System.out.println(var++);
            }
        });
        Thread t2 = new Thread(() -> {
            while (var < 1000) {
                System.out.println(var++);
            }
        });
        Thread t3 = new Thread(() -> {
            while (var < 10000) {
                System.out.println(var++);
            }
        });
        t1.start();
        t2.start();
        t3.start();
    }
}