Revalidate/validate + repaint to add a number of JTextFields

Question

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class FIFO_MenuBar extends JMenuBar {
String[] prgsItems = new String[] {"Start Simulation", "Reset", "Exit"};
String[] typeItems = new String[] {"FCFS", "HRRN", "PR", "RR", "SJF", "SRTN"};
public JTextField jTxF0[];
int k = 0;
public FIFO_MenuBar () {
JMenu progress = new JMenu("Program to...");
JMenu typemenu = new JMenu("Simulations Types");
ActionListener listen = new ActionListener() {
public void actionPerformed(ActionEvent event) {
if (event.getActionCommand() == "Start Simulation") {
k = Integer.parseInt(JOptionPane.showInputDialog("Enter number of process"));
jTxF0 = new JTextField[k];
JPanel panel = new JPanel();
for (int i = 0; i < jTxF0.length; i++) {
jTxF0[i] = new JTextField(10);
panel.add(jTxF0);
for (int i = 0; i < prgsItems.length; i++) {
JMenuItem item = new JMenuItem(prgsItems[i]);
item.addActionListener(listen);
//System.out.println(item.getActionCommand());
progress.add(item);
progress.insertSeparator(2);
for (int j = 0; j < typeItems.length; j++) {
JMenuItem item = new JMenuItem(typeItems[j]);
item.addActionListener(listen);
typemenu.add(item);
typemenu.insertSeparator(1);
typemenu.insertSeparator(5);
JMenuItem item;
add(progress);
add(typemenu);
public static void main(String s[]) {
JFrame frame = new JFrame("CPU Simulation");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setJMenuBar(new FIFO_MenuBar());
frame.pack();
frame.setVisible(true);
No idea why it wouldn't create the number of JTextFields that I want when I go from "Program to..." --> "Start Simulatioin"...
It just wouldn't add the JTextField for me...

Answer 1

you generally don't want anything in main() except to kick off the program
FIFO_MenuBar is a menuBar, so you don't want to be putting your frame code in there,
best to just pass any needed references.
here's your code split into 2 classes with the necessary reference passed to FIFO....
see if you can follow what's happening
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class FIFO_MenuBar extends JMenuBar {
  String[] prgsItems = new String[] {"Start Simulation", "Reset", "Exit"};
  String[] typeItems = new String[] {"FCFS", "HRRN", "PR", "RR", "SJF", "SRTN"};
  public JTextField jTxF0[];
  int k = 0;
  public FIFO_MenuBar (final JPanel panel) {
    JMenu progress = new JMenu("Program to...");
    JMenu typemenu = new JMenu("Simulations Types");
    ActionListener listen = new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        if (event.getActionCommand() == "Start Simulation") {
          k = Integer.parseInt(JOptionPane.showInputDialog("Enter number of process"));
          jTxF0 = new JTextField[k];
          //JPanel panel = new JPanel();
          for (int i = 0; i < jTxF0.length; i++) {
            jTxF0[i] = new JTextField(10);
            panel.add(jTxF0);
panel.revalidate();
panel.repaint();
for (int i = 0; i < prgsItems.length; i++) {
JMenuItem item = new JMenuItem(prgsItems[i]);
item.addActionListener(listen);
//System.out.println(item.getActionCommand());
progress.add(item);
progress.insertSeparator(2);
for (int j = 0; j < typeItems.length; j++) {
JMenuItem item = new JMenuItem(typeItems[j]);
item.addActionListener(listen);
typemenu.add(item);
typemenu.insertSeparator(1);
typemenu.insertSeparator(5);
JMenuItem item;
add(progress);
add(typemenu);
class GUI
public void buildGUI()
JPanel framePanel = new JPanel();
framePanel.setPreferredSize(new Dimension(400,300));
JFrame frame = new JFrame("CPU Simulation");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(framePanel);
frame.setJMenuBar(new FIFO_MenuBar(framePanel));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
public static void main(String s[])
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new GUI().buildGUI();