Simple Calculator, GUI

import javax.swing.JOptionPane;

class apples{
    public static void main(String args[]){

        String fn = JOptionPane.showInputDialog("Please enter 1st number: ");
        String sn = JOptionPane.showInputDialog("Please enter 2nd number: ");

        int num1 = Integer.parseInt(fn);
        int num2 = Integer.parseInt(sn);

        int sum = num1 + num2;

        JOptionPane.showMessageDialog(null, "The answer is " + sum, "Your sum", JOptionPane.PLAIN_MESSAGE);

    }
}