Untitled

import javax.swing.*;
import java.awt.event.*;

public class SubtractNumbers extends JFrame {
    JTextField t1 = new JTextField(5), t2 = new JTextField(5);
    JLabel result = new JLabel("Result: ");

    SubtractNumbers() {
        setLayout(new java.awt.FlowLayout());
        add(t1);
        add(t2);
        add(result);
        addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                try {
                    int n1 = Integer.parseInt(t1.getText());
                    int n2 = Integer.parseInt(t2.getText());
                    result.setText("Result: " + (n1 - n2));
                } catch (Exception ex) {
                    result.setText("Invalid input");
                }
            }
        });
        setSize(200, 100);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
    }

    public static void main(String[] args) {
        new SubtractNumbers();
    }
}