Calculator for adding 2 numbers using Gui

package makecalculator;

import javax.swing.JFrame;
import javax.swing.JButton;

import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class CALCULATOR extends JFrame
{
    CALCULATOR()
    {
        /* Constructing Frame */
        JFrame frame = new JFrame();

        frame.setTitle("MY CALCULATOR");
        frame.setBounds(0, 0, 400, 400);
        frame.setVisible(true);
        frame.setLayout(null);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);

        /* Construction Text Fields */
        final TextField tf1 = new TextField();
        tf1.setBounds(50, 300, 250, 20);
        frame.add(tf1);
        final TextField tf2 = new TextField();
        tf2.setBounds(50, 200, 250, 20);
        frame.add(tf2);
        final TextField tf3 = new TextField();
        tf3.setBounds(50, 100, 250, 20);
        frame.add(tf3);
        /* Construction Text Fields - Adding TExt fields */





        /*Construction button*/
        JButton b1 = new JButton();
        b1.setLocation(50,50);
        b1.setSize(50,50);
        b1.setText("+");
        /*Construction button - Adding Actions*/
        b1.addActionListener
        (
             new ActionListener()
             {
                 public void actionPerformed(ActionEvent e)
                 {
                    String s1 = tf1.getText();
                    String s2 = tf2.getText();
                    int num1=Integer.parseInt(s1);
                    int num2=Integer.parseInt(s2);
                    int sum = num1+num2;
                    tf3.setText(Integer.toString(sum));
                 }

             }
        );
        /*Construction button - adding button b1*/
        frame.add(b1);
    }
}
public class MakeCalculator
{
    public static void main(String[] args)
    {
        CALCULATOR c = new CALCULATOR();
    }
}