Main.java

package com.example;

public class Main
{

    private static int foo = 1;

    public static void main(String[] args) throws InterruptedException
    {
        new Thread(() -> foo = 2).start();
        new Thread(() -> foo = 3).start();
        new Thread(() -> System.out.println(foo)).start();
        new Thread(() -> System.out.println(foo)).start();

        Thread.sleep(1000);
    }
}