Program to perform numerical operations like calculator using Swing components

/* Program : 15
   Program to perform numerical operations like calculator using Swing components
   Development Status : Completed and Tested
   Developed by : Malhar Vora
   Developed on : 20-11-2010
   Email        : vbmade2000@gmail.com
   WebSite  : www.malhar2010.blogspot.com
 *****************************************************************/
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class P15 extends JFrame implements ActionListener
{

 
 JLabel lblFirst = null;
 JLabel lblSecond = null;
 JLabel lblResult=null;
 JTextField txtFirst =null;
 JTextField txtSecond =null;
 JTextField txtResult=null;
 JButton btnAdd=null;
 JButton btnSub=null;
 JButton btnMul=null;
 JButton btnDiv=null; 
 
 
 P15()
 {
 
  lblFirst = new JLabel("First Value");
  lblSecond = new JLabel("Second Value");
  lblResult = new JLabel("Result");
  txtFirst = new JTextField();
  txtSecond = new JTextField();
  txtResult = new JTextField();
  btnAdd = new JButton("+");
  btnSub = new JButton("--");
  btnMul = new JButton("X");
  btnDiv = new JButton("/");
  
  
  setTitle("Program 15 - Developed by Malhar Vora");
  setSize(280,250);
  setVisible(true);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
  setLayout(null);
  
  lblFirst.setBounds(20,10,100,50);
  txtFirst.setBounds(110,20,100,30);
  lblSecond.setBounds(20,50,100,50);
  txtSecond.setBounds(110,60,100,30);
  lblResult.setBounds(20,90,100,50);
  txtResult.setBounds(110,100,100,30);
  btnAdd.setBounds(20,150,50,50);
  btnSub.setBounds(80,150,50,50);
  btnMul.setBounds(140,150,50,50);
  btnDiv.setBounds(200,150,50,50);
  txtResult.setEditable(false);
  
  
  
  getContentPane().add(lblFirst);
  getContentPane().add(txtFirst);
  getContentPane().add(lblSecond);
  getContentPane().add(txtSecond);
  getContentPane().add(lblResult);
  getContentPane().add(txtResult);
  getContentPane().add(btnAdd);
  getContentPane().add(btnSub);
  getContentPane().add(btnMul);
  getContentPane().add(btnDiv);
  
  
  btnAdd.addActionListener(this);
  btnSub.addActionListener(this);
  btnMul.addActionListener(this);
  btnDiv.addActionListener(this);
  
  
      
 }
 
 public void actionPerformed(ActionEvent ae)
 {
  String cmd = ae.getActionCommand();
  
  if(cmd.equals("+"))
  {
    int a,b,c;
    a = Integer.parseInt(txtFirst.getText());
    b = Integer.parseInt(txtSecond.getText());
    c = a+b;
    txtResult.setText("" + c);    
  }
  else if(cmd.equals("--"))
  {
    int a,b,c;
    a = Integer.parseInt(txtFirst.getText());
    b = Integer.parseInt(txtSecond.getText());
    c = a-b;
    txtResult.setText("" + c);  
  }
  else if(cmd.equals("X"))
  {
    int a,b,c;
    a = Integer.parseInt(txtFirst.getText());
    b = Integer.parseInt(txtSecond.getText());
    c = a*b;
    txtResult.setText("" + c);  
  }
  else if(cmd.equals("/"))
  {
    int a,b,c;
    try
    {
      a = Integer.parseInt(txtFirst.getText());
      b = Integer.parseInt(txtSecond.getText());
      c = a/b;
      txtResult.setText("" + c);  
    }
    catch(Exception e)
    {
      txtResult.setText("Error in division");
    }
  }
 }
 
 
 
 public static void main(String []str)
 {
  P15 p = new P15();
 }
}