Hi Friend,

Try the following code:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class TotalInterest extends JFrame
{
        TotalInterest(){
        JLabel lab1=new JLabel("Principal");
        final JTextField text1=new JTextField(20);

        JLabel lab2=new JLabel("Rate of Interest");
        final JTextField text2= new JTextField(20);

        JLabel lab3=new JLabel("Number of Months");
        final JTextField text3=new JTextField(20);

        JButton b=new JButton("Get");
        b.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
            double p=Double.parseDouble(text1.getText());
            double r=Double.parseDouble(text2.getText())/100;
            double t=Double.parseDouble(text3.getText())/12;

            double interest=p*r*t;
            JOptionPane.showMessageDialog(null, "Total Interest is: "+interest);

            }
        });
           setLayout(null);
           lab1.setBounds(10,10,100,20);
           text1.setBounds(150,10,200,20);
           lab2.setBounds(10,40,100,20);
           text2.setBounds(150,40,200,20);
           lab3.setBounds(10,70,120,20);
           text3.setBounds(150,70,200,20);
           b.setBounds(150,110,70,20);
           add(lab1);
           add(text1);
           add(lab2);
           add(text2);
           add(lab3);
           add(text3);
           add(b);
           setVisible(true);
           setSize(400,200);
        }
    public static void main(String[] args) 
    {
    new TotalInterest();
        }
}

Thanks