import java.awt.*;
import javax.swing.*;    public class Main extends JFrame
{
    int x,y,w,h;       
    static String input;
    
    public Main()
    {
        super("Draw");
        x=Integer.parseInt(JOptionPane.showInputDialog("X="));
        y=Integer.parseInt(JOptionPane.showInputDialog("Y="));
        w=Integer.parseInt(JOptionPane.showInputDialog("width="));
        h=Integer.parseInt(JOptionPane.showInputDialog("height="));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(700,400);
        setVisible(true);
        repaint();
    }
    
    public void paint(Graphics g)
    {
        g.setColor(Color.black);
        if(input.compareTo("a")==0)
        {
            g.drawOval(x, y, w, h);
        }
        if(input.compareTo("b")==0)
        {
            g.drawRect(x, y, w, h);
        }
    }
    
    public static void main(String[] args) 
    {
        input=JOptionPane.showInputDialog("a.矩形\n"  
                                         "b.橢圓形\n"
                                        );
        Main work=new Main();
    }
}

引言: 請問要加什麼才能讓視窗調整大小後圖形還能在?