Java 2D 화면 그리기

import javax.swing.*;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.geom.Line2D;
import java.awt.Color;

class Test extends JPanel{

  public static void main(String[] args){
            JFrame frame = new JFrame();

            Test app = new Test();
            frame.getContentPane().add(app);

            frame.setBackground(Color.white);
            frame.setResizable(false);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setBounds(0, 0, 400, 400);
            frame.setTitle("2D描画");
            frame.setVisible(true);
            Insets insets = frame.getInsets();  // 設定すべき値を求めるためのインスタンス化
            frame.setSize(400 + insets.left + insets.right,
                          400 + insets.top + insets.bottom); // 画面サイズ設定
          }

          public void paintComponent(Graphics g){
            Graphics2D g2 = (Graphics2D)g;
            g2.setColor(Color.black);

            g.drawLine(200,  0,200,400);
            g.drawLine(  0,200,400,200);

            drawPoint(g2);
            drawCircle(g2);
            drawEllipse(g2);
          }

          public void drawPoint(Graphics2D g2){
              int x=400, y=0; 
              for(int i=0; i<400; i++){
                  g2.fillRect(x, y, 1, 1);
                  x -= 1;
                  y += 1;
              }
          }

          public void drawCircle(Graphics2D g2){
              double x, y, cx=200, cy=200, r=100;
              for(int i = 0; i < 720; i++){
                  x = r*Math.sin(i)+cx;
                  y = r*Math.cos(i)+cy;
                  g2.draw(new Line2D.Double(x, y, x+0.1, y+0.1));
              }
          }

          public void drawEllipse(Graphics2D g2){
              double x, y, cx=200, cy=200, r=100;
              for(int i=0; i<720; i++){
                  x = r*Math.sin(i)+cx;
                  y = (r*Math.cos(i))/2+cy;
                  g2.draw(new Line2D.Double(x, y, x, y));
              }
          }
}