JTable size problems due to layout/grid...how can I fix?

Question

This is my code. When the button "Modify Entries" is pressed, it shows a JTable that imports a file called, "entries.data". The items in this file can be read and saved using this program. The problem is that the table is so small when it first opens. How can I set all my buttons to the very bottom of the form and make the table take up more space at the top? It looks to me as if this layout is treating it with the same dimensions as the buttons'.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import java.util.*;
import java.io.*;
public class CPT extends JPanel implements ActionListener
    protected JButton ModifyEntriesButton, ViewEntriesButton, SearchEntriesButton, SaveButton, BackButton;
    private final static String newline = "\n";
    private DefaultTableModel model;
    public CPT ()
        super (new GridLayout (10, 0));
        model = new PropertiesModel ("entries.data");
        ModifyEntriesButton = new JButton ("Modify Entries");
        ModifyEntriesButton.setVerticalTextPosition (AbstractButton.TOP);
        ModifyEntriesButton.setHorizontalTextPosition (AbstractButton.LEFT);
        ModifyEntriesButton.setToolTipText ("Click this button to modify database entries.");
        ModifyEntriesButton.setMnemonic (KeyEvent.VK_M);
        ModifyEntriesButton.setActionCommand ("ModifyEntries");
        ModifyEntriesButton.addActionListener (this);
        ViewEntriesButton = new JButton ("View Entries");
        ViewEntriesButton.setVerticalTextPosition (AbstractButton.CENTER);
        ViewEntriesButton.setHorizontalTextPosition (AbstractButton.LEFT);
        ViewEntriesButton.setToolTipText ("Click this button to add view all database entries.");
        ViewEntriesButton.setMnemonic (KeyEvent.VK_V);
        ViewEntriesButton.setActionCommand ("ViewEntries");
        ViewEntriesButton.addActionListener (this);
        SearchEntriesButton = new JButton ("Search Entries");
        SearchEntriesButton.setVerticalTextPosition (AbstractButton.BOTTOM);
        SearchEntriesButton.setHorizontalTextPosition (AbstractButton.LEFT);
        SearchEntriesButton.setToolTipText ("Click this button to search through all database entries.");
        SearchEntriesButton.setMnemonic (KeyEvent.VK_S);
        SearchEntriesButton.setActionCommand ("SearchEntries");
        SearchEntriesButton.addActionListener (this);
        SaveButton = new JButton ("Save");
        SaveButton.setVerticalTextPosition (AbstractButton.TOP);
        SaveButton.setHorizontalTextPosition (AbstractButton.RIGHT);
        SaveButton.setToolTipText ("Click this button to save database entries.");
        SaveButton.setMnemonic (KeyEvent.VK_S);
        SaveButton.setActionCommand ("Save");
        SaveButton.addActionListener (this);
        BackButton = new JButton ("Back");
        BackButton.setVerticalTextPosition (AbstractButton.BOTTOM);
        BackButton.setHorizontalTextPosition (AbstractButton.RIGHT);
        BackButton.setToolTipText ("Click this button to return to the main menu.");
        BackButton.setMnemonic (KeyEvent.VK_B);
        BackButton.setActionCommand ("Back");
        BackButton.addActionListener (this);
        add (ModifyEntriesButton);
        add (ViewEntriesButton);
        add (SearchEntriesButton);
    class PropertiesModel extends DefaultTableModel
        public PropertiesModel (String filename)
            addColumn ("Item Number");
            addColumn ("Description");
            addColumn ("Price");
            //Fill model with data from property file
            Properties props = readFile (filename);
            if (props != null)
                Enumeration coll = props.keys ();
                while (coll.hasMoreElements ())
                    String property = (String) coll.nextElement ();
                    String value = props.getProperty (property, "");
                    addRow (new Object[]
                        property, value
    private Properties readFile (String filename)
        try
            Properties props = new Properties ();
            props.load (new FileInputStream (filename));
            return props;
        catch (IOException ioe)
            return null;
    private boolean saveFile (String filename)
        try
            Properties props = new Properties ();
            for (int i = 0 ; i < model.getRowCount () ; i++)
                props.put (model.getValueAt (i, 0), model.getValueAt (i, 1));
            props.store (new FileOutputStream (filename), null);
            return true;
        catch (IOException ioe)
            return false;
    public void actionPerformed (ActionEvent e)
        if ("ModifyEntries".equals (e.getActionCommand ()))
            removeAll ();
            add (new JScrollPane (new JTable (model)), BorderLayout.CENTER);
            add (SaveButton);
            add (BackButton);
            invalidate ();
            updateUI ();
        if ("ViewEntries".equals (e.getActionCommand ()))
            removeAll ();
            add (BackButton);
            invalidate ();
            updateUI ();
        if ("SearchEntries".equals (e.getActionCommand ()))
            removeAll ();
            add (BackButton);
            invalidate ();
            updateUI ();
        if ("Back".equals (e.getActionCommand ()))
            removeAll ();
            add (ModifyEntriesButton);
            add (ViewEntriesButton);
            add (SearchEntriesButton);
            invalidate ();
            updateUI ();
        if ("Save".equals (e.getActionCommand ()))
            if (saveFile ("entries.data"))
                JOptionPane.showMessageDialog (null, "File saved successfully.");
            else
                JOptionPane.showMessageDialog (null, "File could not be saved!");
    // Create the GUI and show it. For thread safety,
    // this method should be invoked from the
    // event-dispatching thread.
    private static void createAndShowGUI ()
        //Make sure we have nice window decorations.
        JFrame.setDefaultLookAndFeelDecorated (true);
        //Create and set up the window.
        JFrame frame = new JFrame ("Swisha Computer House");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        //Create and set up the content pane.
        JComponent newContentPane = new CPT ();
        newContentPane.setOpaque (true); //content panes must be opaque
        frame.setContentPane (newContentPane);
        //Display the window.
        frame.pack ();
        frame.setSize (300, 300);
        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 ();
}Hey, and if anyone knows how to get the first column's numbers from the file to show up in descending order (1 through to, say, 500), please let me know.
Thank you for any help.

Answer 1

It looks to me as if this layout is treating it with the same dimensions as the buttons'.Thats the way a GridLayout works.
Read the Swing tutorial on [url http://java.sun.com/docs/books/tutorial/uiswing/layout/visual.html]How to Use Layout Managers. You can mix an match individual Layout Managers to get the effect desired.
I would suggest you need to change your design. Your code for continually removing and adding components is not the best design. You should probably have a panel with all your buttons. Then you would have different panels for each of your sub functions. The display of these panels would be controlled by a Card Layout. The tutorial has working examples of this.
You can't use a Properties file to save data from the table (at least not the way you are attempting to use it). I gave you a solution in your last posting.