在Java中从数组中随机绘制多个圆圈

Question

我还是Java新手。这是我的程序，当你点击我的菜单下的'Slow'时，随机地在我的阵列中的不同位置画一个'mole'。但是我无法得到任何东西。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.*;

public class WackAmole extends JFrame{

    MolePanel molePanel = new MolePanel();
    JMenu file = new JMenu("File");
     JMenuItem exitItem = new JMenuItem("EXIT GAME"); 
     JMenu gameSpeed = new JMenu("Game Speed");
     JMenuItem slow= new JMenuItem("Slow");
     JMenuItem normal = new JMenuItem("Normal");
     JMenuItem fast = new JMenuItem("Fast");
     JLabel score = new JLabel("Score");
     JLabel time = new JLabel("Elasped Time");

    public void createGUI(){

    JPanel scoreBoard = new JPanel(new FlowLayout(FlowLayout.CENTER));
         scoreBoard.add(score);
         scoreBoard.add(time);   

        JFrame frame = new JFrame("WHACK 'A' MOLE");
        frame.getContentPane().setLayout(new BorderLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(scoreBoard);

        gameSpeed.add(slow);
        gameSpeed.add(normal);
        gameSpeed.add(fast);

        file.add(exitItem);
        file.add(gameSpeed);

        JMenuBar menuBar = new JMenuBar();
        menuBar.add(file);
        frame.setJMenuBar(menuBar);

        slow.addActionListener(new ButtonListener());
        exitItem.addActionListener(new ButtonListener());
        frame.setPreferredSize(new Dimension(600,400));
        frame.pack();
        frame.setVisible(true);
 }


public static void main (String[] args){
    //show the frame
    WackAmole wackAmole = new WackAmole();       
    wackAmole.createGUI();      
}

public class ButtonListener implements ActionListener{
    public void actionPerformed (ActionEvent e){
        if (e.getActionCommand().equals("EXIT GAME")){
            System.exit(0);
        }
        if (e.getActionCommand().equals("Slow")){
            // this button works... it receives input
            molePanel.aMole();
        }           
    }
}
}

文件2：

import java.awt.Dimension;
import java.awt.Graphics;
import java.util.Random;
import javax.swing.*;
public class MolePanel extends JPanel{
Random random = new Random();
private static final long serialVersionUID = 1L;
private int xCoord[] = {-1, -1};
private int yCoord[] = {-1, -1};
private Dimension preferredSize = new Dimension(300,200);

int x = random.nextInt(2);
int y = random.nextInt(2);
public void aMole (){

     xCoord[x] +=25;
     yCoord[y] +=25;
    repaint();
}

@Override
public Dimension getPreferredSize(){
    return preferredSize;
}
protected void paintComponent (Graphics mole){
    if(xCoord[x] < 0 || yCoord[y] < 0){
        xCoord[x] = 25;
        yCoord[y] = 25;
    }
    super.paintComponent(mole);
   mole.fillOval(xCoord[x], yCoord[y], 10, 10);     
   }        
}