How to draw a polygon using GUI in Java

Problem Description

How to draw a polygon using GUI?

Solution

Following example demonstrates how to draw a polygon by creating Polygon() object. addPoint() & drawPolygon() method is used to draw the Polygon.

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

public class Main extends JPanel {
   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      Polygon p = new Polygon();
      for (int i = 0; i < 5; i++) p.addPoint((int) (
         100 + 50 * Math.cos(i * 2 * Math.PI / 5)),(int) (100 + 50 * Math.sin(
         i * 2 * Math.PI / 5)));
      g.drawPolygon(p);
   }
   public static void main(String[] args) {
      JFrame frame = new JFrame();
      frame.setTitle("Polygon");
      frame.setSize(350, 250);
      
      frame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
      Container contentPane = frame.getContentPane();
      contentPane.add(new Main());
      frame.setVisible(true);
   }
}

Result

The above code sample will produce the following result.

Polygon is displayed in a frame.

The following is an another sample example to draw a polygon using GUI.

import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

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

public class Panel extends JPanel {
   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      Polygon p = new Polygon();
      for (int i = 0; i < 5; i++) p.addPoint((int) (
         100 + 50 * Math.cos(i * 2 * Math.PI / 5)),(int) (
         100 + 50 * Math.sin(i * 2 * Math.PI / 5)));
      
      g.drawPolygon(p);
   } 
   public static void main(String[] args) {
      JFrame frame = new JFrame();
      frame.getContentPane().setBackground(Color.YELLOW); 
      frame.setTitle("DrawPoly");
      frame.setSize(350, 250);
      frame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         } 
      }); 
      Container contentPane = frame.getContentPane();
      contentPane.add(new Panel());
      frame.show();
   }
}

The above code sample will produce the following result.

Polygon is displayed in a frame.