combining two strings using java

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

//////////////////////////////////////////////////////////////// CombineName
public class CombineName extends JFrame {
    //=================================================== instance variables
    private JTextField _fNameTf        = new JTextField(8);
    private JTextField _lNameTf        = new JTextField(8);
    private JTextField _combinedNameTf = new JTextField(14);
    
    //================================================================= main
    public static void main(String[] args) {
        JFrame window = new CombineName();   // Create window.
    }
    
    //========================================================== constructor
    public CombineName() {
        //... 1. Create or set attributes of components.
        _combinedNameTf.setEditable(false);  // Don't let user change output.
        JButton combineBtn = new JButton("Combine");
        
        //... 2. Add listener(s).
        combineBtn.addActionListener(new CombineAction());
        
        //... 3. Create a panel, set layout, and add components to it.
        JPanel content = new JPanel();
        content.setLayout(new FlowLayout());
        content.add(new JLabel("First"));
        content.add(_fNameTf);
        content.add(new JLabel("Last"));
        content.add(_lNameTf);
        content.add(combineBtn);
        content.add(new JLabel("Combined Name"));
        content.add(_combinedNameTf);
        
        //... 4. Set the content panel of window and perform layout.
        this.setContentPane(content);
        this.setTitle("CombineName Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.pack();                       // Do layout.
        this.setLocationRelativeTo(null);  // Center window.
        this.setVisible(true);
    }
    
    ///////////////////////////////////// inner listener class CombineAction
    class CombineAction implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            //... Get text from the text fields, combine, set text.
            //    Please make this program do something interesting.
            String first = _fNameTf.getText();
            String last  = _lNameTf.getText();
            String combined = last + ", " + first;  // Trivial logic!!!
            _combinedNameTf.setText(combined);
        }
    }
}