Thread: Help in showing the elements

I write this code in one class but it doesn't show any elements ( button , labels ) all elements , but when I put it in two classes one the main and another one it works fine .

Here is the code :

package averageprogram;
 
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
 
public class AverageProgram extends JFrame{
private int num = 0;
     private String userCo = "";
    private JButton[] buttons;
    private JButton btn = new JButton("Click");
     private JButton btn1 = new JButton("Calculate Average");
    private  Container cp = getContentPane();
     private  JTextField userInput = new JTextField(30);
     private  JLabel label = new JLabel("Please enter the number of Courses: ");
     private  JTextField[] userInput1;
     private  JTextField[] userInput2;
 
     private  JLabel[] label1;
     private  JLabel[] label2;
     private  JLabel label3 = new JLabel("");
      private JPanel panel = new JPanel();
      private JPanel panel1 = new JPanel();
 
        private  int s1= 70;
        private int s2= 88;
        private int s3= 77;
        private double total = s1+ s2+ s3;
 
 
    public static void main(String[] args) {
 
 
      JFrame frame = new JFrame("frame");
     frame.setSize(600, 400);       
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("program");
    }
 
      public AverageProgram()
    {
 
         cp.add(panel);
     cp.add(panel1,BorderLayout.SOUTH);
 
         panel.add(label);
       panel.setLayout(new FlowLayout());
         panel.add(userInput);
        panel.add(btn);
      panel1.add(btn1);
 
 
 
 
 
 
        ButtonWatcher handler = new ButtonWatcher();
        btn.addActionListener(handler);
 
        ButtonWatcher1 handler1 = new ButtonWatcher1();
        btn1.addActionListener(handler1);
 
 
    }
     private class ButtonWatcher implements ActionListener {
 
        public void actionPerformed(ActionEvent a)
        {
 
               try {
             userCo = userInput.getText();
 
                num = Integer.parseInt(userCo);
          label1 = new JLabel[num];
               label2 = new JLabel[num];
               userInput1 = new JTextField[num];
               userInput2 = new JTextField[num];
               }
               catch (Exception exception) {
                                    JOptionPane.showMessageDialog(null, "Error Input");
                                }
            for(int i = 0; i<num; i++)
        {
              label1[i] = new JLabel("Course Name " + i);
 
             userInput1[i] = new JTextField(10);
               userInput1[i].setHorizontalAlignment(JTextField.CENTER);
                label2[i] = new JLabel("Course Grade " + i);
              userInput2[i] = new JTextField(10);
                userInput2[i].setHorizontalAlignment(JTextField.CENTER);
        }
 
             for(int i=0; i < num; ++i)
        {
           panel.add(label1[i]);
               panel.add(userInput1[i]);
 
            panel.add(label2[i]);
                 panel.add(userInput2[i]);
 
        }
 
           SwingUtilities.updateComponentTreeUI(cp);  
        }
 
    }
 
      private class ButtonWatcher1 implements ActionListener {
 
        public void actionPerformed(ActionEvent a)
        {
       try
       {
                 if (userInput.getText().isEmpty()) {
                        String message = "You must enter a number of your courses first";
                        JOptionPane.showMessageDialog(new JFrame(), message, "Dialog",
                                JOptionPane.ERROR_MESSAGE);
                 }
 
                 else
                 {
            int numOfCourses = 3;
            double avg = 0.0;
            double temp = 0.0;
 
              for(int i = 0; i<num; i++)
        {
 
            numOfCourses++;
            temp = Double.parseDouble(userInput2[i].getText());
            total  = total + temp;
        }
 
                 panel.add(label3);
                 avg = total / numOfCourses;
                  avg =Math.round(avg * 10.0) / 10.0;
                 label3.setText("The result is : " + avg + " %" );
 
 
        }
        }
        catch (Exception exception) {
                                    JOptionPane.showMessageDialog(null, "Error Input");
                                }
        }
 
 
}
 
 
}

It really take so much time for me to wrote it . sorry for bad formatting .
If you copy the code and paste it , and run it , it will show only blank form without any elements . I don't know what I missing ...

I use only one class , why I should create an instance ...

Can you help me more , I don't get it really .
I write this in the main method ?

 AverageProgram test = new AverageProgram();

and what's next ?

Nothing happened, If I add these code in the main method it show me there is error :

  cp.add(panel);
     cp.add(panel1,BorderLayout.SOUTH);
 
         panel.add(label);
       panel.setLayout(new FlowLayout());
         panel.add(userInput);
        panel.add(btn);
      panel1.add(btn1);
 
 
        ButtonWatcher handler = new ButtonWatcher();
        btn.addActionListener(handler);
 
        ButtonWatcher1 handler1 = new ButtonWatcher1();
        btn1.addActionListener(handler1);

--- Update ---

Can anyone please help me ...

Ok now it's show all the elements thank you , but there is one more problem the style if the program is changed look before :
https://i.imgur.com/01w485N.png

and after :
https://i.imgur.com/2XZ6SGm.png

why this happened?

You must understand first I was used two classes one for the main and one contain all the JFrame components , after I use one class (the main inside it )
this problem happened ...

No now I used one class only , and this is the whole code : (can you please tell me where to change to make the layout looks like in the above picture ? ...

package averageprogram;
 
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
 
public class AverageProgram extends JFrame{
 
private int num = 0;
     private String userCo = "";
    private JButton[] buttons;
    private JButton btn = new JButton("Click");
     private JButton btn1 = new JButton("Calculate Average");
    private  Container cp = getContentPane();
     private  JTextField userInput = new JTextField(30);
     private  JLabel label = new JLabel("Please enter the number of Courses that you have completed in Fall17/18 : ");
     private  JTextField[] userInput1;
     private  JTextField[] userInput2;
 
     private  JLabel[] label1;
     private  JLabel[] label2;
     private  JLabel label3 = new JLabel("");
      private JPanel panel = new JPanel();
      private JPanel panel1 = new JPanel();
 
        private  int s1 = 70;
        private int s2 = 88;
        private int s3 = 77;
        private double total = s1+ s2+ s3;
 
 
    public static void main(String[] args) {
 
       AverageProgram test = new AverageProgram();
     test.setSize(600, 400);       
        test.setVisible(true);
        test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        test.setTitle("Name");
 
 
    }
 
      public AverageProgram()
    {
      cp.add(panel);
     cp.add(panel1,BorderLayout.SOUTH);
 
       panel.setLayout(new FlowLayout());
         panel.add(label);
 
         panel.add(userInput);
        panel.add(btn);
      panel1.add(btn1);
 
 
        ButtonWatcher handler = new ButtonWatcher();
        btn.addActionListener(handler);
 
        ButtonWatcher1 handler1 = new ButtonWatcher1();
        btn1.addActionListener(handler1);
 
 
 
    }
     private class ButtonWatcher implements ActionListener {
 
        public void actionPerformed(ActionEvent a)
        {
 
               try {
             userCo = userInput.getText();
 
                num = Integer.parseInt(userCo);
          label1 = new JLabel[num];
               label2 = new JLabel[num];
               userInput1 = new JTextField[num];
               userInput2 = new JTextField[num];
               }
               catch (Exception exception) {
                                    JOptionPane.showMessageDialog(null, "Error Input");
                                }
            for(int i = 0; i<num; i++)
        {
              label1[i] = new JLabel("Course Name " + i);
 
             userInput1[i] = new JTextField(10);
               userInput1[i].setHorizontalAlignment(JTextField.CENTER);
                label2[i] = new JLabel("Course Grade " + i);
              userInput2[i] = new JTextField(10);
                userInput2[i].setHorizontalAlignment(JTextField.CENTER);
        }
 
             for(int i=0; i < num; ++i)
        {
 
           panel.add(label1[i]);
               panel.add(userInput1[i]);
 
            panel.add(label2[i]);
                 panel.add(userInput2[i]);
 
        }
 
           SwingUtilities.updateComponentTreeUI(cp);  
        }
 
    }
 
      private class ButtonWatcher1 implements ActionListener {
 
        public void actionPerformed(ActionEvent a)
        {
       try
       {
                 if (userInput.getText().isEmpty()) {
                        String message = "You must enter a number of your courses first";
                        JOptionPane.showMessageDialog(new JFrame(), message, "Dialog",
                                JOptionPane.ERROR_MESSAGE);
                 }
 
                 else
                 {
            int numOfCourses = 3;
            double avg = 0.0;
            double temp = 0.0;
 
              for(int i = 0; i<num; i++)
        {
 
            numOfCourses++;
            temp = Double.parseDouble(userInput2[i].getText());
            total  = total + temp;
        }
 
                 panel.add(label3);
                 avg = total / numOfCourses;
                  avg =Math.round(avg * 10.0) / 10.0;
                 label3.setText("The result is : " + avg + " %" );
 
 
        }
 
        }
        catch (Exception exception) {
                                    JOptionPane.showMessageDialog(null, "Error Input");
                                }
        }  
}   
}

Ok thank you a lot man , I will try to solve it . Thanks so much for helping .