JAVA30 - プログラム倉庫

import java.awt.*;
import javax.swing.*;
public class ex30 extends JFrame {
   public static void main (String args[]) {
      new ex30();
   }

   public ex30() {
      setDefaultCloseOperation(EXIT_ON_CLOSE);
      getContentPane().add(new MyJPanel());
      setSize(800,500);
      setTitle("練習");
      setVisible(true);
   }
}

class MyJPanel extends JPanel {
   public MyJPanel() {setBackground(Color.white);}
   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      g.setColor(Color.green);
      for (int z=100;z<=500;++z) {
         g.drawLine(z,500-z,z,500-z);
      }
      g.setColor(Color.red);
      for (int z=0;z<=799;++z) {
         g.drawLine(z,500-400,z,500-400);
      }
   }
}