Java 二次元 回転行列

Javaで回転行列のプログラムを作成しました。

コード

package J3D;

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

public class J3D2 extends JPanel{

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

    J3D2 app = new J3D2();
    frame.getContentPane().add(app);
    frame.setBackground(Color.BLACK);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setBounds(0, 0, 400, 400);
    frame.setTitle("あいうえお");
    frame.setVisible(true);
    Insets insets = frame.getInsets();
    frame.setSize(400 + insets.left + insets.right,
    		      400 + insets.top + insets.bottom);
  }

  public void paintComponent(Graphics g){
	Graphics2D g2 = (Graphics2D)g;
	
	int x = 1,y = 1;
	
	g2.setColor(Color.BLUE);
	g2.draw(new Line2D.Double(200,0,200,400));
	g2.draw(new Line2D.Double(0,200,400,200));
	
	drawCircle(g2);
  }
  public void drawCircle(Graphics2D g2){
	  
      double x , y , cx = 200, cy = 200, r = 100;
      for(int i = 0; i < 12; i++){
          x = r * Math.sin(Math.toRadians(30*i)) + cx;
          y = r * Math.cos(Math.toRadians(30*i)) + cy;
          g2.setColor(Color.GREEN);
          g2.draw(new Line2D.Double(x, y, x + 0.1, y + 0.1));
      }
  }
}

実行環境
・Mac versin 10.10.2
・eclipse