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 1. Modify the addX method using ReentrantLock to get the desired output.
时间: 2023-12-19 07:05:16 浏览: 30
Sure, here's the modified `addX` method using `ReentrantLock` to get the desired output:
```
import java.util.concurrent.locks.ReentrantLock;
class Game {
private static final int DELAY = 500;
private int x;
private final ReentrantLock lock = new ReentrantLock();
public Game() {
x = 0;
}
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();
}
}
}
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 `ReentrantLock` is used to ensure that only one thread can access the `addX` method at a time. This prevents race conditions where multiple threads can update the `x` value at the same time, leading to incorrect results.