Java Code:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.TexturePaint;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class TransformDemo extends JPanel {
  public void init() {
    setBackground(Color.white);
  }

  public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    Rectangle rect = new Rectangle(5,5,200,200);
    int w = getSize().width;
    int h = getSize().height;
    AffineTransform saveXform = g2.getTransform();
    AffineTransform toCenterAt = new AffineTransform();
    toCenterAt.translate(w / 2 - (rect.width / 2), h / 2 - (rect.height / 2));
    g2.transform(toCenterAt);
    g2.fill(rect);
    g2.transform(saveXform);
  }

  public static void main(String s[]) {
    JFrame f = new JFrame();
    f.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    TransformDemo p = new TransformDemo();
    f.getContentPane().add("Center", p);
    p.init();
    f.pack();
    f.setSize(new Dimension(300, 300));
    f.show();
  }

}