Menghitung Luas Segitiga - Fernando

package LuasSegiTiga;

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class Segitiga extends JFrame {

    /**
     *E
     */
    private static final long serialVersionUID = 1L;
    int num1;
    int num2;
    float num3;
    private JLabel label1;
    private JLabel label2;
    private JButton calculate;
    private JTextField textfield1;
    private JTextField textfield2;

    public static void main (String args[]) {
        Segitiga gui = new Segitiga();
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        gui.setSize(200, 230);
        gui.setVisible(true);
        gui.setTitle("Segitiga");
    }

    public Segitiga(){
        setLayout(new FlowLayout());

        label1 = new JLabel ("Alas Segitiga");
        add(label1);

        textfield1 = new JTextField (15);
        add(textfield1);

        label1 = new JLabel ("Tinggi Segitiga");
        add(label1);

        textfield2 = new JTextField (15);
        add(textfield2);

        label1 = new JLabel ("Hasil:");
        add(label1);

        label2 = new JLabel ("", SwingConstants.CENTER);
        label2.setPreferredSize(new Dimension(150, 20));
        add(label2);

        calculate = new JButton ("Hitung!");
        add(calculate);


        event event = new event();
        calculate.addActionListener(event);
    }

    public class event implements ActionListener {
        public void actionPerformed(ActionEvent event){
            num1 = Integer.parseInt(textfield1.getText());
            num2 = Integer.parseInt(textfield2.getText());
            num3 = (float)(num1*num2*0.5);
            label2.setText(String.valueOf(num3));
        }
    }

}