Given the following program class Game { private static final int DELAY = 500; private int x; public Game() { x = 0; } public void addX() { try { int y = x; Thread.sleep((int) (DELAY * Math.random())); y += 1; x = y; System.out.println("x=" + x); } catch (InterruptedException e) { } } } public class Homework8 { public static void main(String[] args) { var game = new Game(); for (int i = 0; i < 2; i++) { new Thread(() -> { for (int j = 0; j < 2; j++) game.addX(); }).start(); } } } The output could be x=1 x=1 x=2 x=2 or x=1 x=2 x=1 x=2 However, we desire the output to be x=1 x=2 x=3 x=4 Modify the addX method using ReentrantLock to get the desired output.

To achieve the desired output `x=1 x=2 x=3 x=4`, we can use the `ReentrantLock` class to synchronize the `addX()` method. Here's how we can modify the `Game` class:

import java.util.concurrent.locks.ReentrantLock;

class Game {
    private static final int DELAY = 500;
    private int x;
    private ReentrantLock lock;

    public Game() {
        x = 0;
        lock = new ReentrantLock();
    }

    public void addX() {
        lock.lock();
        try {
            int y = x;
            Thread.sleep((int) (DELAY * Math.random()));
            y += 1;
            x = y;
            System.out.println("x=" + x);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}

In this modified `Game` class, we have added a `ReentrantLock` instance variable named `lock`, and we have used it to synchronize the `addX()` method. The `lock()` method is called to acquire the lock before executing the critical section of the method, and the `unlock()` method is called to release the lock.

With this modification, the output of the program will always be `x=1 x=2 x=3 x=4`.