import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.Line2D;

public class DrawTriangleUsingLine2D extends JApplet {
    public void init() {
    setBackground(Color.lightGray);
  }
    public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D) g;
    g2d.setPaint(Color.red);
    g2d.draw(new Line2D.Double(50,150,150,150 ));
  g2d.draw(new Line2D.Double(50,50,150,150 ));
  g2d.draw(new Line2D.Double(50,50,50,150 ));
    }
    public static void main(String s[]) {
    JFrame frame = new JFrame("Show Triangle");
    JApplet applet = new DrawTriangleUsingLine2D();
    frame.getContentPane().add("Center", applet);
    applet.init();
    frame.setSize(300, 250);
    frame.show();
  }
}