我的布局键盘上的空格按钮大小不会调整大小

I can resize the whole buttons but its NOT what I want.. the whole point is to be resize just the space bar.. :)

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Arrays;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class example extends JFrame 
{  
    //Individual keyboard rows  
    String firstRow[] = {"~","1","2","3","4","5","6","7","8","9","0","-","+","BackSpace"};
    String secondRow[] = {"Tab","Q","W","E","R","T","Y","U","I","O","P","[","]","\"};
    String thirdRow[] = {"Caps","A","S","D","F","G","H","J","K","L",":",""","Enter"};
    String fourthRow[] = {"Shift","Z","X","C","V","B","N","M",",",".","?","   ^" };
    String fifthRow[]={"               " ,"<" ,"v",">" };
    String strText = "";
    //all keys without shift key press
    String noShift="`1234567890-=qwertyuiop[]\asdfghjkl;'zxcvbnm,./";
    //special characters on keyboard that has to be addressed during key press
    String specialChars ="~-+[]\;',.?";

    //Jbuttons corresponding to each individual rows 
    JButton first[];
    JButton second[];
    JButton third[];
    JButton fourth[];
    JButton fifth[];


    //Driver main method to start the application 
    public static void main(String[] args) {
        //launch typing tutor
        new example().setVisible(true);
    }

    // No argument constructor to create frame
    public example()
    {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //set size of the content pane ie frame
        this.getContentPane().setPreferredSize(new Dimension(1200,275));

        initWidgets();
    }


    // Method to initialize frame component 
    private void initWidgets()
    {

        //set the layout and place component in place and pack it 
        setLayout(new BorderLayout());
        //Various panel for the layout 
        JPanel jpNorth = new JPanel();
        JPanel jpCenter = new JPanel();
        JPanel jpKeyboard = new JPanel();
        JPanel jpNote = new JPanel();
        add( jpNorth, BorderLayout.NORTH);
        add( jpNote);
        add( jpCenter, BorderLayout.CENTER);
        add(jpKeyboard, BorderLayout.SOUTH);

        //layout for keyboard 
        jpKeyboard.setLayout(new GridLayout(5,1));
        //pack the components
        pack();

        //paint first keyboard row  and add it to the keyboard
        first = new JButton[firstRow.length];
        //get the panel for the  row
        JPanel p = new JPanel(new GridLayout(1, firstRow.length));
        for(int i = 0; i < firstRow.length; ++i) 
        {
            JButton b= new JButton(firstRow[i]);
            b.setPreferredSize(new Dimension(100,50));
            first[i] = b;
            p.add(first[i]);
        }
        jpKeyboard.add(p);

        //paint second keyboard row  and add it to the keyboard
        second = new JButton[secondRow.length];
        //get the panel for the  row
        p = new JPanel(new GridLayout(1, secondRow.length));
        for(int i = 0; i < secondRow.length; ++i) 
        {
            second[i] = new JButton(secondRow[i]);
            p.add(second[i]);

        }
        jpKeyboard.add(p);

        //paint third keyboard row  and add it to the keyboard
        third = new JButton[thirdRow.length];
        //get the panel for the  row
        p = new JPanel(new GridLayout(1, thirdRow.length));
        for(int i = 0; i < thirdRow.length; ++i)
        {
            third[i] = new JButton(thirdRow[i]);
            p.add(third[i]);
        }
        jpKeyboard.add(p);

        //paint fourth keyboard row  and add it to the keyboard
        fourth = new JButton[fourthRow.length];
        //get the panel for the  row
        p = new JPanel(new GridLayout(1, fourthRow.length));
        for(int i = 0; i < fourthRow.length; ++i)
        {
            fourth[i] = new JButton(fourthRow[i]);
            p.add(fourth[i]);
            if(i==fourthRow.length-2)
                p.add(new JPanel());

        }
        p.add(new JPanel());
        jpKeyboard.add(p);

        //paint the fifth row
        fifth = new JButton[fifthRow.length];
        //get the panel for the  row
        p = new JPanel(new GridLayout(1, fifthRow.length));
        //put empty panel for layout adjustments 
        for(int i = 0; i < 1; ++i)
        {
            JPanel  spacePanel = new JPanel();
            p.add(spacePanel);
        }
        //draw the buttons 
        for(int i = 0; i < fifthRow.length; ++i)
        {
            if(i==1) //space bar panel
            {
                JButton b = new JButton(fifthRow[i]);
                b.setPreferredSize(new Dimension(400,10));
                b.setBounds(10, 10, 600, 100);
                fifth[i]=b;
                //add empty panels for layout 
                p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());p.add(new JPanel());
            }
            else
            {
                fifth[i]=new JButton(fifthRow[i]);
            }
            if(i==0) //first black panel
            {
                   //place a black panel at first
                   JPanel  spacePanel = new JPanel();
                   p.add(spacePanel);
            }
            p.add(fifth[i]);

        }
        jpKeyboard.add(p);

        } //end of initWidgets   

}//end of class

好吧，如果你们中的任何人可以指导我，我将非常感激，如果你们需要任何澄清或更多信息，请告诉我.. :)