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

public class Weight extends JFrame implements ActionListener {
    JTextField name = new JTextField();
    JTextField weight = new JTextField();
    JTextField length = new JTextField();

    public Weight() {
        setLayout(new GridLayout(3,2));
        JLabel nameLbl = new JLabel("Namn:");
        JLabel weightLbl = new JLabel("Vikt:");
        JLabel lengthLbl = new JLabel("Längd:");

        add(nameLbl);
        add(name);
        add(weightLbl);
        add(weight);
        add(lengthLbl);
        add(length);

        name.addActionListener(this);        
        weight.addActionListener(this);
        length.addActionListener(this);

        setPreferredSize(new Dimension(300,200));
        pack();
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void actionPerformed(ActionEvent e) {
        String nameString = name.getText();
        double tmpWeight = Double.parseDouble(weight.getText());
        double tmpLength = Double.parseDouble(length.getText());
        String output = String.format("Hej %s. Du väger %fkg/cm.",nameString, tmpWeight/tmpLength);
        JOptionPane.showMessageDialog(null, output);
    }

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

}