http://www.dreamincode.net/forums/topic/224851-adding-two-numbers/

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;


public class Ass140 extends JFrame implements ActionListener
{
 JLabel l1,l2,l3;
 JButton b1;
 JTextField t1,t2,t3;

 Ass140()
 {
  l1=new JLabel("INPUT 1");
  l2=new JLabel("INPUT 2");
  l3=new JLabel("OUTPUT");
  b1=new JButton("BUTTON 1");

  t1=new JTextField(10);
  t2=new JTextField(10);
  t3=new JTextField(10);

  add(l1);
  add(t1);
  add(l2);
  add(t2);
  add(l3);
  add(t3);
  add(b1);

  b1.addActionListener(this);

  setSize(200,200);
  setLayout(new FlowLayout());
  setTitle("Assignment 139");
 }

 public void actionPerformed(ActionEvent ae)
 {
  float a,b,c;
  if(ae.getSource()==b1)
  {
   a=Float.parseFloat(t1.getText());
   b=Float.parseFloat(t2.getText());
   c=a+b;
   t3.setText(String.valueOf(c));

  }


 }

 public static void main(String args[])
 {
  Ass140 a=new Ass140();
  a.setVisible(true);
  a.setLocation(200,200);

 }

}