9 button frame based application Create a Frame-based application that displays an array of nine buttons on a Panel

import java.awt.*;
import java.awt.event.*;
 
public class MF extends Frame {
    String course[]={"Course1","Course2","Course3","Course4","Course5","Course6","Course7","Course8","Course9"};
    TextField txtField = new TextField();
    Button[] but=new Button[9];
    Label label1 = new Label("Press the button, the corresponding course name will be shown in the text field!");
   
    MF() {
    	super("9 button frame based application");
        addWindowListener(closer);
        
        Panel pan = new Panel();
        pan.setLayout(new GridLayout(3,3));
        
        actionListener l1 = new actionListener();
        
        for (int i=0;i<9;i++){
        	but[i]=new Button(course[i]);
        	pan.add(but[i],i);
        	but[i].addActionListener(l1);
        }
        
        this.add(label1,BorderLayout.NORTH);
        this.add(pan, BorderLayout.CENTER);        
        this.add(txtField,BorderLayout.SOUTH);
        
        this.setSize(600,300);
        setVisible(true);  
    }
 
    private class actionListener implements ActionListener{ 
        public void actionPerformed(ActionEvent e){ 
           for( int i=0;i<9; i++) 
        	   if (e.getSource().equals(but[i])) 
        		   txtField.setText(but[i].getLabel()) ;
        } 
     }
    
    private WindowListener closer = new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    };
 
    public static void main(String[] args) {
        new MF();
    }
}