java – GUI未按预期显示

package Chapter22Collections;
import javax.swing.*;
import java.awt.*;

public class Exercise226 extends JFrame {
    private JButton jbSort;
    private JButton jbReverse;
    private JButton jbAdd;
    private JButton jbShuffle;
    private JLabel jlAddnum;
    private JTextArea jTextDisplay;
    private JTextField jTextAdd;

    public Exercise226() {
        jbSort = new JButton("Sort");
        jbReverse = new JButton("Reverse");
        jbShuffle = new JButton("Shuffle");
        jbAdd = new JButton("Add");
        jlAddnum = new JLabel("Add number here: ");
        jTextDisplay = new JTextArea();
        jTextAdd = new JTextField(8);

        setLayout(new BorderLayout());

        JPanel p1 = new JPanel(new GridLayout(1,3));
        p1.add(jlAddnum);
        p1.add(jTextAdd);
        p1.add(jbAdd);

        JPanel p2 = new JPanel(new GridLayout(1,3));
        p2.add(jbSort);
        p2.add(jbReverse);
        p2.add(jbShuffle);

        add(p1,BorderLayout.NORTH);
        add(jTextDisplay,BorderLayout.CENTER);    
        add(p2,BorderLayout.SOUTH);
    }

    public static void main(String... args) {

        Exercise226 gui = new Exercise226();
        gui.setTitle("Numbers");
        gui.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        gui.setSize(300,200);
        gui.setLocationRelativeTo(null);
        gui.setVisible(true);   

    }     
}