求助！显示结果有问题，要拉动边框才会显示出来

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ImproveProgramme extends JFrame{
  
     JLabel label = new JLabel("Enter a new message");
     JTextField jtf = new JTextField(10);
   
   
    public static void main(String[] args) {
        ImproveProgramme frame = new ImproveProgramme();
        frame.setTitle("improve 15_2");
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300,200);
        frame.setVisible(true);
   
    }
    public ImproveProgramme(){
        JPanel p = new JPanel();
        
     
        p.add(label);
        p.add(jtf);
        jtf.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
            
               jtf.requestFocusInWindow();   
            }   
        });
        jtf.addKeyListener(new KeyAdapter(){
            public void keyReleased(KeyEvent e){
               if(e.getKeyCode()==KeyEvent.VK_ENTER){
            
                    JLabel jlb = new JLabel(jtf.getText());
                        add(jlb);
        
               }
            
               
            }
            
    });
   
    add(p);

    }
}