在Java中同时按下两个键

Question

我正在编写一个游戏，并且有2个玩家同时玩游戏。如果两个玩家同时按下一个键并且玩家释放了他的钥匙，则另一个玩家没有移动。

import java.awt.*;
import javax.swing.*;
import java.awt.*;
import javax.swing.*;
import java.applet.*;
import java.awt.event.*;
import java.util.ArrayList;

public class MultiKey extends Applet implements KeyListener {
    int x = 240, y = 240;
    int x2 = 240, y2 = 240;
    public ArrayList<Integer> keysDown;

    public void init() {
        this.addKeyListener(this);
        keysDown = new ArrayList<Integer>();
        setFocusable(true);
    }

    public void paint(Graphics g) {
        setSize(500, 500);
        g.setColor(Color.GREEN);
        g.fillRect(x, y, 50, 50);
        g.setColor(Color.BLUE);
        g.fillRect(x2 - 50, y2 - 50, 50, 50);
        g.drawString(keysDown + "", 100, 100);
    }

    public void keyPressed(KeyEvent e) {
        if (!keysDown.contains(e.getKeyCode())) {
            keysDown.add(new Integer(e.getKeyCode()));
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_UP))) {
            y = y - 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_DOWN))) {
            y = y + 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_LEFT))) {
            x = x - 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_RIGHT))) {
            x = x + 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_W))) {
            y2 = y2 - 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_S))) {
            y2 = y2 + 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_A))) {
            x2 = x2 - 5;
        }
        if (keysDown.contains(new Integer(KeyEvent.VK_D))) {
            x2 = x2 + 5;
        }
        repaint();
    }

    public void keyReleased(KeyEvent e) {
        keysDown.remove(new Integer(e.getKeyCode()));
    }

    public void keyTyped(KeyEvent e) {
    }
}