Java by API/java.awt.geom/RoundRectangle2D

new RoundRectangle2D.Double.Double(double x, double y, double w, double h, double arcw, double arch)

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.RoundRectangle2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class MainClass extends JPanel {
  public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    RoundRectangle2D r = new RoundRectangle2D.Double (10.0, 10.0,
                                                      50.0, 50.0,
                                                      5.0, 5.0);
    g2.draw (r);
  }
  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.getContentPane().add(new MainClass());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(200, 200);
    frame.setVisible(true);
  }
}