java中画直线的问题！！！

import javax.swing.*;
import java.awt.*;
public class ex1_shapes extends JFrame{
/**
* @param args
*/
public ex1_shapes(){
super("实验一:直线、圆弧、多边形");
setSize(500,500);
show();
}
public void paint(Graphics g){
super.paint(g);
//直线演示
g.setColor(Color.BLUE);
g.drawLine(10, 10, 80, 150);
g.drawString("直线演示",50,50);
// 圆弧演示 显示“CS”
g.setColor(Color.green);
g.drawArc(180, 50, 50, 90, 30, 300); //c
g.drawArc(250, 50, 50, 45, 30,250); g.drawArc(250, 95, 50, 45, 90, -270); //S
g.drawString("圆弧演示",330,50);
//多边形 五角星
g.setColor(Color.RED);
int[] xpoints1={100,120,200,136,160,100,40,64,0,80};
int[] ypoints1={210,270,270,326,410,357,410,326,270,270};
g.drawPolygon(xpoints1, ypoints1, 10);
g.drawString("折线段演示",80,440);
//填充五角星
int[] xpoints2={350,370,450,386,410,350,290,314,250,330};