No error but can't see after logging in

[boybackup]

no error but i can't see anything after log in.. i dunno why.. please help.. here's the code.

LoginDemo.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
class Login extends JFrame implements ActionListener
{
 JButton SUBMIT;
 JPanel panel;
 JLabel label1,label2;
 final JTextField  text1,text2;
  Login()
  {
  label1 = new JLabel();
  label1.setText("Username:");
  text1 = new JTextField(15);

  label2 = new JLabel();
  label2.setText("Password:");
  text2 = new JPasswordField(15);
 
  SUBMIT=new JButton("SUBMIT");
  
  panel=new JPanel(new GridLayout(4,1));
  panel.add(label1);
  panel.add(text1);
  panel.add(label2);
  panel.add(text2);
  panel.add(SUBMIT);
  add(panel,BorderLayout.CENTER);
  SUBMIT.addActionListener(this);
  setTitle("LOGIN FORM");
  }
 public void actionPerformed(ActionEvent e)
  {
  String value1=text1.getText();
  String value2=text2.getText();
  if (value1.equals("java") && value2.equals("sample")) {
int i=0;
NextPage page=new NextPage();
page.setVisible(true); 
JButton[] buttons = new JButton[4];
panel=new JPanel(new GridLayout(4,6));
String  b[]={"S","McFloat","Fries","Burger",};
for(i = 0; i < buttons.length; i++) {
buttons[i] = new JButton(b[i]);
buttons[i].setSize(80, 80);
buttons[i].setActionCommand(b[i]);
buttons[i].addActionListener(new ActionListener(){
    
public void actionPerformed(ActionEvent e) {
String choice = e.getActionCommand();
JOptionPane.showMessageDialog(null, "You have clicked: "+choice);
setVisible(true); 
  }
});
panel.add(buttons[i]);
}
  }
  else{
  System.out.println("enter the valid username and password");
  JOptionPane.showMessageDialog(this,"Incorrect login or password",
  "Error",JOptionPane.ERROR_MESSAGE);
  }
}
}
 class LoginDemo
{
  public static void main(String arg[])
  {
  try
  {
  Login frame=new Login();
  frame.setSize(300,100);
  frame.setVisible(true);
  }
  catch(Exception e)
  {JOptionPane.showMessageDialog(null, e.getMessage());}
  }
}


NextPage.java

import javax.swing.*;
import java.awt.*;
 
class NextPage extends JFrame
{
  NextPage()
 {
 setDefaultCloseOperation(javax.swing.
  WindowConstants.DISPOSE_ON_CLOSE);
 setTitle("Welcome");
 setSize(400, 200);
  }
 }

[Norm]

i can't see anything after log in.

What do you expect to see?
Add some printlns to the code to show where the execution is going. Be sure to print out the values of any variables that are used to make decisions.