import javax.swing.*;
import java.awt.*;
public class X2Function extends JFrame
{
public X2Function()
{
add(new X2FunctionPanel());
}
public static void main(String[] args)
{
X2Function frame=new X2Function();
frame.setSize(400,250);
frame.setTitle("绘制y=x2的函数");
frame.setLocationRelativeTo(null);//center
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
class X2FunctionPanel extends JPanel
{
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
//画x轴
g.drawLine(20,150,getWidth()-20,150);
//x箭头
g.drawLine(getWidth()-30,140,getWidth()-20,150);
g.drawLine(getWidth()-30,160,getWidth()-20,150);
//“x”
g.drawString("X",getWidth()-10,150);
//画y轴
g.drawLine(200,getHeight()-20,200,20);
g.drawLine(190,30,200,20);
g.drawLine(210,30,200,20);
g.drawString("Y",220,30);
//画函数图像
Polygon p=new Polygon();
double scaleFactor=0.01;
for(int x=-100;x<=100;x++)
{
p.addPoint(x+200,150-(int)(scaleFactor*x*x));
}
g.drawPolyline(p.xpoints,p.ypoints,p.npoints);
}
/*public Dimension getPreferredSize()
{
return new Dimension(200,200);
}*/
}