Mit jelent a this?

public class Szocikk {
  JFrame frame = new JFrame();
  datumPanel dp = new DatumPanel();

}
class Datumpanel {
  JPanel datum = new JPanel;
  add.Label
  add.TextField
  stb
  datum.add(elrendezés_tipus);
}

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

/* FrameDemo.java requires no other files. */
public class FrameDemo {
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("FrameDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        //JLabel emptyLabel = new JLabel("");
        //emptyLabel.setPreferredSize(new Dimension(575, 100));
        //frame.getContentPane().add(emptyLabel, BorderLayout.CENTER);


    JPanel panelFelso = new JPanel(new FlowLayout(FlowLayout.LEFT));
    JPanel panelAlso = new JPanel(new FlowLayout());


    Container cp = frame.getContentPane();


    cp.add(panelFelso, BorderLayout.PAGE_START);
    cp.add(panelAlso, BorderLayout.PAGE_END);


    JLabel napLabel = new JLabel("Nap");
    JTextField napTextField = new JTextField("Days", 8);
    JLabel honapLabel = new JLabel("Hónap");
    String[] honapok = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
    JComboBox honapComboBox = new JComboBox(honapok);
    
    //honapComboBox.setSelectedIndex(12);
    //honapComboBox.addActionListener();
    
    JLabel evLabel = new JLabel("Év");
    JTextField evTextField = new JTextField("Év", 4);


    panelFelso.add(napLabel);
    panelFelso.add(napTextField);
    panelFelso.add(honapLabel);
    panelFelso.add(honapComboBox);
    panelFelso.add(evLabel);
    panelFelso.add(evTextField);


    JLabel alsoLabel = new JLabel("Alsó Panel");
    panelAlso.add(alsoLabel);


    panelFelso.setPreferredSize(new Dimension(575, 100));
    panelAlso.setPreferredSize(new Dimension(575, 100));
        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }


    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}