java 五子棋 怎么感觉有东西盖住了啊？？

[幼儿园校长]

package wzq.panel;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JFrame;
import javax.swing.JPanel;

import wzq.chess.Chess;


public class ChessPanel extends JPanel implements MouseListener {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	int x,y;
	int X,Y;
	public int getX() {
		return X;
	}
	public void setX(int x) {
		X = x;
	}
	public int getY() {
		return Y;
	}
	public void setY(int y) {
		Y = y;
	}

	int num[][] = new int[15][15];
	
	public int CovertXY(int x){
		if(x<40){
			x =1;
			return x * 40 -20;
		}else if(x %40 >20){
			x = x/40;
			return x*40 +20;
		}
		x = x /40;
		return x * 40 - 20;
	}
	
		
	
	
	public Chess chess = new Chess();
	

	public ChessPanel(){
		addMouseListener(this);
	}
	public static void main(String[] args) {
		JFrame frame = new JFrame("棋盘");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		ChessPanel cp =new ChessPanel();
		cp.setBackground(Color.ORANGE);
		frame.getContentPane().add(cp, "Center");
		frame.setBounds(1000, 200, 620, 650);
		frame.setVisible(true);
	}
	
	public void paintComponent(Graphics g){
		super.paintComponent(g);
		for(int i=0;i<chess.getChess_row();i++){
			for(int j=0;j<chess.getChess_cloumn();j++){
				g.setColor(Color.black);
				g.drawRect(i*40, j*40, chess.chess_grid, chess.chess_grid);
			}
		}
		if(num[x][y] == 0){
			g.setColor(Color.black);
			g.fillOval(getX(), getY(), 40, 40);
		}
		
	}
	
	@Override
	public void mouseClicked(MouseEvent e) {}

	@Override
	public void mousePressed(MouseEvent e) {
		
		X= CovertXY(e.getX());
		Y= CovertXY(e.getY());
		System.out.println();
		System.out.println(e.getX());
		System.out.println(e.getY());
		
		
		System.out.println(X);
		System.out.println(Y);
		
		
		
		repaint();
		
		
	}
	

	@Override
	public void mouseReleased(MouseEvent e) {}

	@Override
	public void mouseEntered(MouseEvent e) {}

	@Override
	public void mouseExited(MouseEvent e) {	}
	
}

好不容易解决了校准问题 这棋子怎么到一定范围他就不显示了 好像给什么盖住了 我也不清楚 怎么会这样呢？？求大神帮忙解决 谢谢

[幼儿园校长]

快来人啊

[scmod]

是不是因为棋盘是在棋子之后重画的... 不大熟..