Rotate the coordinate in Java

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
//  w w  w .j  av  a2s. c o m
import javax.swing.JComponent;
import javax.swing.JFrame;

class MyCanvas extends JComponent {
  public void paint(Graphics g) {
    AffineTransform atrans = null;

    Graphics2D g2d = (Graphics2D) g;
    atrans = AffineTransform.getRotateInstance(Math.PI / 4, 50, 50);

    if (atrans != null)
      g2d.setTransform(atrans);

    g2d.fillRect(50, 50, 100, 50);
  }
}

public class Main {
  public static void main(String[] a) {
    JFrame window = new JFrame();
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setBounds(30, 30, 450, 450);
    window.getContentPane().add(new MyCanvas());
    window.setVisible(true);
  }
}