你试过把它加到相框里吗？添加（cp）； import java.awt.BorderLayout; import java.awt.GridLayout; import java.awt.Component; import java.awt.FlowLay

你试过把它加到相框里吗？添加（cp）；

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.Font;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JComboBox;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JScrollPane;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextArea;
import javax.swing.SwingConstants;
import javax.swing.JOptionPane;

import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Scanner;
import java.util.Formatter;
import java.io.IOException;
import java.io.File;
import java.io.FileOutputStream;

import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class Ch5PA1 extends JFrame {

    private String[] courseDescription = new String[5];
    private JLabel courseLabel;
    private JButton closeProgram;
    private JTextArea displayArea;
    private Font largeFont;
    private ImageIcon computer;
    private JComboBox<String> coursesCombo;
    private JPanel p1, p2;

    public static void main(String[] args) {

        JFrame.setDefaultLookAndFeelDecorated(true);
        Ch5PA1 frame = new Ch5PA1();
        frame.setSize(700, 400);
        frame.setTitle("CIT Courses and Descriptions");
        frame.setVisible(true);
    }

    public Ch5PA1() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        createIcon();
        createLabel();
        createTextArea();
        createCombo();
        createButton();
        createPanels();

        JComponent cp = (JComponent) getContentPane();
        cp.setLayout(new BorderLayout(0, 40));
        cp.setBorder(new EmptyBorder(20, 20, 20, 20));

        cp.add(p1, BorderLayout.WEST);
        cp.add(new JScrollPane(displayArea), BorderLayout.CENTER);
        cp.add(p2, BorderLayout.CENTER);
    }

    public void createIcon() {
        computer = new ImageIcon("computer.jpg");
    }

    public void createLabel() {
        courseLabel = new JLabel("Select a Course From the List", SwingConstants.CENTER);
        courseLabel.setIcon(new ImageIcon("computer.jpg"));
    }

    public void createTextArea() {
        displayArea = new JTextArea(10, 20);
        displayArea.setLineWrap(true);
        displayArea.setEditable(false);

        displayArea.setBorder(new EmptyBorder(20, 20, 20, 20));
    }

    public void createCombo() {
        coursesCombo = new JComboBox<String>();
        coursesCombo.addItem("CIT 110");
        coursesCombo.addItem("CIT 111");
        coursesCombo.addItem("CIT 149");
        coursesCombo.addItem("CIT 170");
        coursesCombo.addItem("CIT 249");

        coursesCombo.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent e) {
                setDisplay(coursesCombo.getSelectedIndex());
            }
        });

        setDisplay(0);
    }

    public void createButton() {
        closeProgram = new JButton("Close Program");
        closeProgram.setFont(largeFont);
        closeProgram.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });
    }

    public void createPanels() {
        p1 = new JPanel();
        p1.setLayout(new BorderLayout());
        p1.add(coursesCombo, BorderLayout.NORTH);
        p1.add(closeProgram, BorderLayout.SOUTH);

        p1.setBorder(new EmptyBorder(20, 40, 20, 40));

        p2 = new JPanel();
        p2.setLayout(new GridLayout(2, 1, 20, 40));
        p2.add(courseLabel);
        p2.add(displayArea);
        add(p2, BorderLayout.CENTER);

        p2.setBorder(new EmptyBorder(20, 40, 20, 40));
    }

    public void createDescriptions() {
        for (int i = 0; i < courseDescription.length; i++) {
            courseDescription[i] = getDescription(i);
        }
    }

    public String getDescription(int i) {
        StringBuilder result = new StringBuilder();

        try {
            Scanner input = new Scanner(new File("text/description" + i + ".txt"));

            while (input.hasNext()) {
                result.append(input.nextLine() + '\n');
            }
        } catch (IOException ex) {
            JOptionPane.showMessageDialog(null, "Error loading file! Check name   and location of file.");
        }

        return result.toString();
    }

    public void setDisplay(int index) {
        displayArea.setText(getDescription(index));
    }
}

public Ch5PA1() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    createIcon();
    createLabel();
    createTextArea();
    createCombo();
    createButton();
    createPanels();

    JComponent cp = (JComponent) getContentPane();
    cp.setLayout(new BorderLayout(0, 40));
    cp.setBorder(new EmptyBorder(20, 20, 20, 20));

    cp.add(p1, BorderLayout.WEST);
    cp.add(new JScrollPane(displayArea), BorderLayout.CENTER);
    cp.add(p2, BorderLayout.CENTER);
    // Not added to anything?
}