不知道如何使用外部窗格进行GUI

我有以下2个Java类。我想上三等班。第三类应该是带有两个选项卡的选项卡式窗格。一个选项卡应具有我放置的第一个窗格，第二个选项卡应具有我放置的第二个窗格。我不知道。在我断开计算机之前，请帮助我。我到处搜寻。我已经尝试阅读oracle文档，但我猜它对我没有点击。我已经一遍又一遍地阅读我的文字了.....

package Week4;

import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.text.DecimalFormat;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class OfficeAreaCalculator extends JFrame{

private JFrame mainFrame;
private JButton calculateButton;
private JButton exitButton;
private JTextField lengthField;
private JTextField widthField;
private JTextField areaField;
private JLabel lengthLabel;
private JLabel widthLabel;
private JLabel areaLabel;

public OfficeAreaCalculator()
{
    mainFrame = new JFrame("Office Area Calculator");

    exitButton = new JButton("Exit");
    lengthLabel = new JLabel("Enter the length of the office:");
    widthLabel = new JLabel("Enter the width of the office:");
    areaLabel = new JLabel("Office area:");
    lengthField = new JTextField(5);
    widthField = new JTextField(5);
    areaField = new JTextField(5);
    areaField.setEditable(false);
    calculateButton = new JButton("Calculate");

    Container c = mainFrame.getContentPane();
    c.setBackground(Color.white);
    c.setLayout(new FlowLayout());

    c.add(lengthLabel);
    c.add(lengthField);
    c.add(widthLabel);
    c.add(widthField);
    c.add(areaLabel);
    c.add(areaField);
    c.add(calculateButton);
    c.add(exitButton);

    calculateButton.setMnemonic('C');
    exitButton.setMnemonic('X');

    mainFrame.setSize(260, 150);

    mainFrame.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });

    CalculateButtonHandler chandler = new CalculateButtonHandler();
    calculateButton.addActionListener(chandler);

    ExitButtonHandler ehandler = new ExitButtonHandler();
    exitButton.addActionListener(ehandler);

    FocusHandler fhandler = new FocusHandler();
    lengthField.addFocusListener(fhandler);
    widthField.addFocusListener(fhandler);
    areaField.addFocusListener(fhandler);

    mainFrame.setVisible(true);
}




class CalculateButtonHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e)
    {
        DecimalFormat num = new DecimalFormat(",###.##");
        double width, length, area;
        String instring;

        instring = lengthField.getText();
        if (instring.equals(""))
        {
            instring = ("0");
            lengthField.setText("0");
        }
        length = Double.parseDouble(instring);

        instring = widthField.getText();
        if (instring.equals(""))
        {
            instring = "0";
            widthField.setText("0");
        }
        width = Double.parseDouble(instring);

        area = length * width;
        areaField.setText(num.format(area));

    }

}

class ExitButtonHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e) {
        System.exit(0);
    }       
}

class FocusHandler implements FocusListener
{
    public void focusGained(FocusEvent e)
    {
        if (e.getSource() == lengthField || e.getSource() == widthField)
        {
            areaField.setText("");
        }
        else if (e.getSource() == areaField)
        {
            calculateButton.requestFocus();
        }
    }

    public void focusLost(FocusEvent e)
    {
        if (e.getSource() == widthField)
        {
            calculateButton.requestFocus();
        }
    }
}

public static void main(String arg[])
{
    new OfficeAreaCalculator();
}
}

和

package Week4;

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;


import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

import java.awt.*;


public class DayGUI extends JFrame
{
private JFrame mainFrame;
private JButton cmdGood;
private JButton cmdBad;

public DayGUI(){
    mainFrame = new JFrame("Messages");


    cmdGood = new JButton("Good");
    cmdBad = new JButton("Bad");

    Container c = mainFrame.getContentPane();
    c.setBackground(Color.white);
    c.setLayout(new FlowLayout());

    c.add(cmdGood);
    cmdGood.setBackground(Color.green);
    c.add(cmdBad);
    cmdBad.setBackground(Color.red);

    cmdGood.setMnemonic('G');
    cmdBad.setMnemonic('B');

    mainFrame.setSize(300, 100);

    mainFrame.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    }); 

    ButtonsHandler bhandler = new ButtonsHandler();
    cmdGood.addActionListener(bhandler);
    cmdBad.addActionListener(bhandler);

    mainFrame.setVisible(true);
}

class ButtonsHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e){

        if (e.getSource() == cmdGood)               
            JOptionPane.showMessageDialog(null, "Today is a good day!",
                    "Event Handler Message",
                    JOptionPane.INFORMATION_MESSAGE);

        if (e.getSource() == cmdBad)
            JOptionPane.showMessageDialog(null, "Today is a bad day!",
                    "Event Handler Message",
                    JOptionPane.INFORMATION_MESSAGE);

    }
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    DayGUI app;
    app = new DayGUI();
}

}