graphics有关问题，求高手啊弄了好久还是不会。如果能详细点，就好，多谢

graphics问题，求高手啊，弄了好久还是不会。如果能详细点，就好，谢谢！
import java.awt.*;
import javax.swing.*;;
public class text extends JFrame{
private JLabel panelNorth;
private JPanel panelSouth;
private JButton but_start;
private JButton but_out;
private JPanel pan;
private BorderLayout lay;
public text()
{
setTitle("面板");
lay=new BorderLayout();
setLayout(lay);
lay.setVgap(15);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(400,100,500,550);
init();
setVisible(true);
}

public void repaintComponent(Graphics g)
{
super.paintComponents(g); 
g.setColor(Color.black);
g.drawLine(50,50,100,100);
}

void init()
{
panelNorth=new JLabel("画线！");
panelNorth.setFont(new Font("楷体",30,24));
panelNorth.setForeground(Color.blue);
this.getContentPane().add(panelNorth,BorderLayout.NORTH);


panelSouth=new JPanel();
but_start=new JButton("开始");
but_out=new JButton("退出");
but_start.setFont(new Font("楷体",10,16));
but_out.setFont(new Font("楷体",10,16));
panelSouth.add(but_start);
panelSouth.add(but_out);
this.getContentPane().add(panelSouth,BorderLayout.SOUTH);

pan=new JPanel();
pan.repaint();
this.getContentPane().add(pan,BorderLayout.CENTER);
}
public static void main(String args[])
{
new text();
}
}


不知道怎么使用graphics，画线根本画不了。。。

[解决办法]
改了下，自己看一下区别吧

Java code

import java.awt.*;import javax.swing.*;public class text extends JFrame {    private JLabel panelNorth;    private JPanel panelSouth;    private JButton but_start;    private JButton but_out;    private JPanel pan;    private BorderLayout lay;    public text() {        setTitle("面板");        lay = new BorderLayout();        setLayout(lay);        lay.setVgap(15);        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        setBounds(400, 100, 500, 550);        init();        setVisible(true);    }    void init() {        panelNorth = new JLabel("画线！");        panelNorth.setFont(new Font("楷体", 30, 24));        panelNorth.setForeground(Color.blue);        this.getContentPane().add(panelNorth, BorderLayout.NORTH);        panelSouth = new JPanel();        but_start = new JButton("开始");        but_out = new JButton("退出");        but_start.setFont(new Font("楷体", 10, 16));        but_out.setFont(new Font("楷体", 10, 16));        panelSouth.add(but_start);        panelSouth.add(but_out);        this.getContentPane().add(panelSouth, BorderLayout.SOUTH);        pan = new JPanel() {            @Override            public void paintComponent(Graphics g) {                super.paintComponent(g);                g.setColor(Color.black);                g.drawLine(50, 50, 100, 100);            }        };        this.getContentPane().add(pan, BorderLayout.CENTER);    }    public static void main(String args[]) {        new text();    }}