Develop Reference

Java JLabel background color not working?

I'm learning how to create application in Java.
I'm having trouble getting the JLabel to have a background color whilst the JPanel is white, behind it. Also, is there a way to resize the JPanel to half of what the JFrame is?
Any help would be very much appreciated. Thank you.
package PracticeOne;
import java.awt.BorderLayout;
public class PracticeOne {
public static void main(String[] args) {
Frame container = new Frame();
Panel box = new Panel();
Label txt = new Label();
box.add(txt);
container.add(box, BorderLayout.CENTER);
}
}
package PracticeOne;
import javax.swing.JFrame;
public class Frame extends JFrame {
/**
*
*/
private static final long serialVersionUID = 1L;
Frame(){
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(500, 500);
this.setVisible(true);
this.setLocationRelativeTo(null);
this.setTitle("Testing this out");
}
}
package PracticeOne;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JPanel;
public class Panel extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;
public Dimension d = new Dimension(100,100);
Panel(){
this.setSize(d);
this.setAlignmentX(CENTER_ALIGNMENT);
this.setBackground(Color.WHITE);
}
}
package PracticeOne;
import java.awt.Color;
import javax.swing.JLabel;
public class Label extends JLabel {
/**
*
*/
private static final long serialVersionUID = 1L;
Label(){
this.setSize(50, 50);
this.setText("ya boy is working here");
this.setForeground(Color.BLACK);
this.setBackground(Color.ORANGE);
}
}

I'm having trouble getting the JLabel to have a background color whilst the JPanel is white
You need to call setOpaque(true); in your JLabel
Also, is there a way to resize the JPanel to half of what the JFrame is?
You could use a GridLayout, and place 2 JPanels in it, that way, you're going to have 2 JPanels using half the size of your JFrame each.
Also, rename your classes, Panel belongs to the name of a class in AWT, same for Frame and Label, this might confuse your (and whoever reads your code).
Never extend JFrame, instead build your GUI based on JPanels. See extends JFrame vs creating it inside of class and The use of multiple JFrames, Good / Bad practice? The general consensus says it's bad.
Also you should also check Should I avoid the use of setPreferred|Maximum|MinimumSize() in Swing? Again, yes, you should and instead override the getPreferredSize() method.
Don't forget to place your program on the Event Dispatch Thread (EDT) by changing your main() method as follows:
public static void main(String[] args) {
//Java 8 with lambda expressions
SwingUtilities.invokeLater(() ->
//Your code here
);
//Java 7 and below (Or 8 without lambda expressions)
SwingUtilities.invokeLater(new Runnable() {
//Your code here
});
}
Now, with all the above recommendations, your code should now look like this:
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class HalfSizePanelWithLabelInDifferentColor {
private JFrame frame;
private Container contentPane;
private JPanel pane;
private JPanel pane2;
private JLabel label;
private static final Dimension dim = new Dimension(100, 100);
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new HalfSizePanelWithLabelInDifferentColor().createAndShowGui());
}
public void createAndShowGui() {
frame = new JFrame(getClass().getSimpleName());
contentPane = frame.getContentPane();
pane = new JPanel() {
#Override
public Dimension getPreferredSize() {
return dim;
}
};
pane2 = new JPanel();
pane.setOpaque(false);
pane2.setOpaque(false);
pane.setBorder(BorderFactory.createLineBorder(Color.RED));
pane2.setBorder(BorderFactory.createLineBorder(Color.BLUE));
label = new JLabel("Hello World!");
label.setBackground(Color.GREEN);
label.setOpaque(true);
contentPane.setLayout(new GridLayout(2, 1));
pane.add(label);
contentPane.add(pane);
contentPane.add(pane2);
contentPane.setBackground(Color.WHITE);
frame.setContentPane(contentPane);
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
And your output would be like this:
Note that I added some colored borders to show where a pane starts and ends and where the other one starts and ends

How to edit JTextField?

I want to write a simple Swing application with a button and a text field at the bottom. I'm using a JTextField but it is not clickable. I searched on the web and SO, but I could not find a solution. In question How to Set Focus on JTextField?, I found the following :
addWindowListener( new WindowAdapter() {
public void windowOpened( WindowEvent e ){
entry.requestFocus();
}
});
but this does not help. In this other question (How do you set a focus on Textfield in Swing?) I found Component.requestFocus() but this does not work either. I also tried
entry.setFocusable(true);
entry.setEditable(true);
entry.setEnabled(true);
without effects. My code:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class StackSample extends JFrame {
public StackSample() {
initUI();
pack();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
private void initUI() {
JPanel panel = new JPanel(new BorderLayout());
add(panel, BorderLayout.CENTER);
JPanel bottomPanel = new JPanel(new FlowLayout());
panel.add(bottomPanel, BorderLayout.SOUTH);
JButton buttonDraw = new JButton("Draw");
bottomPanel.add(buttonDraw);
JTextField entry = new JTextField();
bottomPanel.add(entry);
setPreferredSize(new Dimension(250, 150));
setLocationRelativeTo(null);
}
private static final long serialVersionUID = 8359448221778584189L;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
MyApp app = new MyApp();
app.setVisible(true);
}
});
}
}

Your JTextField is clickable. The only problem is that it's too small.
This is because you're using FlowLayout, which will make components as small as possible.
One solution is to simply switch to a layout that allows components to fill as much space as possible, such as BoxLayout:
JPanel bottomPanel = new JPanel();
bottomPanel.setLayout(new BoxLayout(bottomPanel,BoxLayout.X_AXIS));

You haven't specified a size for your JTextField, so it defaults to zero characters wide. Try using the constructor that specifies the number of columns.
Also, what is MyApp? I can't see any evidence that your StackSample is ever created or used.

Java JPanel moves slightly on its own + extra

I have a problem. Now I'm working with 3 panels, mainPanel and 2 others ( btnPanel and iconPanel).
So the problem is when I push button "reset" I delete iconPanel and add it again it moves slightly to right on its own. Maybe someone can check my code where the problem?
Also I dont want to create another question so I give 2 extra questions.
Do I delete JPanel properly?
If I delete JPanel with components inside they also will be removed from memory?
P.s. Im beginner so dont judge me :)
Main.java
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class Main extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Made by Mac4s");
frame.setVisible(true);
frame.setSize(310, 654);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.setResizable(false);
MainScreen screenObj = new MainScreen();
screenObj.setPreferredSize(new Dimension(310, 650));
frame.add(screenObj);
}
});
}
}
MainScreen.java
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class MainScreen extends JPanel {
private JButton resetBtn;
private JPanel btnPanel;
private JPanel iconPanel;
public MainScreen() {
JPanel mainPanel = new JPanel(new BorderLayout());
this.setBackground(Color.BLACK);
setBtnPanelAndComp();
setIconPanelAndComp();
add(mainPanel);
}
private void setBtnPanelAndComp() {
btnPanel = new JPanel(new BorderLayout());
btnPanel.setBackground(Color.GREEN);
btnPanel.setPreferredSize(new Dimension(295, 30));
setButtons();
this.add(btnPanel, BorderLayout.NORTH);
}
private void setButtons() {
resetBtn = new JButton("Reset");
resetBtn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
resetIconLabel();
}
});
btnPanel.add(resetBtn, BorderLayout.WEST);
}
private void resetIconLabel() {
this.remove(iconPanel);
this.repaint();
this.revalidate();
setIconPanelAndComp();
}
private void setIconPanelAndComp() {
iconPanel = new JPanel(new BorderLayout());
iconPanel.setBackground(Color.YELLOW);
iconPanel.setPreferredSize(new Dimension(295, 580));
this.add(iconPanel, BorderLayout.SOUTH);
}
}

"the problem is when I push button "reset" I delete iconPanel and add it again it moves slightly to right on its own."
The reason this happens is because a JPanel has a FlowLayout by default. You're trying add to a BorderLayout position that is non-existent.
this.add(iconPanel, BorderLayout.SOUTH);
The FlowLayout has default gaps on the edges, so when you set the size of the frame, those gaps aren't respected. To over come this, it is also preferable to pack() the frame, instead of setSize()
The reason BorderLayout works (doesn't shift) is because preferred sizes aren't respected.
If you set the layout in the constructor to this.setLayout(new BorderLayout()); You won't have the shift.
public MainScreen() {
JPanel mainPanel = new JPanel(new BorderLayout());
this.setLayout(new BorderLayout()); <----
setBtnPanelAndComp();
setIconPanelAndComp();
add(mainPanel);
}
Notes
You should setVisible() after adding components. That's why your frame jumps when you first open it. You are setting the frame visible, then moving it around with the location, and adding components.

JPanels not added to JTabbedPane

For my homework extra credit I am creating a JTabbedPane and adding two Jpanels. I feel like I am very close, but it still does not compile. When I run it, both JPanels open, but the JTabbedPane does not. I get a lot of Unknown Source errors. I suspect that at this point my issue in in the JPanels themselves because they started out being JFrames and I have tried (unsuccessfully I think) to convert the JFrames to JPanels.
JTabbedPaneAssignment is supposed to create the JTabbedPane and populate the two panes with the apps DayGui on one tab and OfficeAreaCalculator on the other. I only include the JTabbedPaneAssignment and DayGui classes here. I apologize if its too much code, I have trimmed off a lot of what I consider extraneous, but there may still be too much.
Here is the calling class JTabbedPaneAssignment
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JTabbedPaneAssignment extends JPanel
{
public JTabbedPaneAssignment()
{
//super(new GridLayout(1, 1));
JTabbedPane tabbedPane = new JTabbedPane();
DayGui pnlDay = new DayGui();
OfficeAreaCalculator pnlOffice = new OfficeAreaCalculator ();
this.add(tabbedPane);
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
tabbedPane.add(panel1,"First panel");
tabbedPane.add(panel2,"Second panel");
//JComponent panel1 = makeTextPanel("Pane #1");
panel1.setPreferredSize(new Dimension(300, 150));
tabbedPane.addTab("DayGui", panel1);
tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
//JComponent panel2 = makeTextPanel("Pane #2");
panel2.setPreferredSize(new Dimension(410, 50));
tabbedPane.addTab("OfficeAreaCalculator", panel2);
tabbedPane.setMnemonicAt(1, KeyEvent.VK_2);
add(tabbedPane);
}
protected JComponent makeTextPanel(String text)
{
JPanel panel = new JPanel(false);
JLabel filler = new JLabel(text);
filler.setHorizontalAlignment(JLabel.CENTER);
panel.setLayout(new GridLayout(1, 1));
panel.add(filler);
return panel;
}
// Create JTabbedPane
private static void createAndShowGUI()
{
// Create and set up the window.
JFrame frame = new JFrame("JTabbedPane");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JTabbedPaneAssignment(), BorderLayout.CENTER);
JTabbedPane DayGui = new JTabbedPane();
JTabbedPane OfficeAreaCalculator = new JTabbedPane();
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
Here is DayGui class. It started out as a JFrame, but I am trying to convert it to a JPanel. I think my issue is in this section of code, but I don't know
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//public class DayGui extends JPanel
public class DayGui extends JPanel
{
private JPanel dayPanel;
private JButton cmdGood;
private JButton cmdBad;
public DayGui()
{
//dayPanel = new JPanel("Messages");
cmdGood = new JButton("Good");
cmdBad = new JButton("Bad");
Container c = dayPanel.getRootPane();
c.setLayout(new FlowLayout());
c.add(cmdGood);
c.add(cmdBad);
dayPanel.setSize(300, 150);
ButtonsHandler bhandler = new ButtonsHandler();
cmdGood.addActionListener(bhandler);
cmdBad.addActionListener(bhandler);
dayPanel.setVisible(true);
dayPanel.getRootPane().setBackground(Color.CYAN);
}
class ButtonsHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == cmdGood)
JOptionPane.showMessageDialog(null, "Today is a good day!",
"Event Handler Message",
JOptionPane.INFORMATION_MESSAGE);
if (e.getSource() == cmdBad)
JOptionPane.showMessageDialog(null, "Today is a bad day!",
"Event Handler Message",
JOptionPane.INFORMATION_MESSAGE);
}
}
}

You have been very ambiguous with your question, and you've posted way more code than anyone here has time to trawl through.
I've made a very small but working JTabbedPane example for you to see the smallest amount of work you need to get it working.
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
public class JTabbedPaneExample extends JFrame{
public JTabbedPaneExample(String title){
super(title);
setSize(800,600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
JTabbedPane tabbedPane = new JTabbedPane();
JPanel panelOne = new JPanel();
JPanel panelTwo = new JPanel();
tabbedPane.add(panelOne,"First panel");
tabbedPane.add(panelTwo,"Second panel");
add(tabbedPane);
}
public static void main(String[] args){
new JTabbedPaneExample("JTP Example").setVisible(true);
}
}
Then running, this code looks like:
If you repeat the same process in your code, and you've still got errors, then the problem is not with your JTabbedPane, but something else.

Okay, here goes a second time. Now you've got the DayGui class up, we notice that you're trying to use dayPanel before you've initialised it. i.e. nowhere do you say dayPanel = new JPanel();. This resulted in a NullPointerException being thrown in your code, screwing up your normal course of exection. Fix this and your DayGui class would run fine at runtime.
Among your codebase, you also do some very funky things, namely start using something but never getting around to finishing it up. An example of this is you extending JPanel, but resorting to using a member variable of type JPanel to do the rest of the work. The suggestion is to scrap the instance variable all together and use the methods you've inherited from extending JPanel.
Now lets move onto your JTabbedPaneAssignment class. Although not terrible, the code is not very readable and it repeats itself in many places (adding your tabbedpanel multiple times). If you were to take this code further into a larger project, maintenance and debugging would quickly become a problem.
For the purposes of showing you how much clutter you had in your code, I've quickly rewritten your provided code to be compilable, and should roughly do what you're working on.
JTabbedPaneAssignment:
import java.awt.BorderLayout;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.SwingUtilities;
public class JTabbedPaneAssignment extends JPanel
{
public JTabbedPaneAssignment()
{
final JTabbedPane tabbedPane = new JTabbedPane();
final DayPanel dayPanel = new DayPanel();
final JPanel officePanel = new JPanel();
tabbedPane.add("DayGui", dayPanel);
tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
tabbedPane.add("OfficeAreaCalculator", officePanel);
tabbedPane.setMnemonicAt(1, KeyEvent.VK_2);
add(tabbedPane);
}
// Create JTabbedPane
private static void createAndShowGUI()
{
// Create and set up the window.
JFrame frame = new JFrame("JTabbedPane");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JTabbedPaneAssignment(), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
DayGui - renamed as DayPanel:
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class DayPanel extends JPanel {
public DayPanel() {
super();
setBackground(Color.CYAN);
final JButton goodButton = new JButton("Good");
final JButton badButton = new JButton("Bad");
ActionListener listener = new DayPanel.ButtonsHandler();
goodButton.addActionListener(listener);
badButton.addActionListener(listener);
add(goodButton);
add(badButton);
}
class ButtonsHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
final String command = ((JButton) e.getSource()).getActionCommand();
if (command.equals("Good")) {
showMessage("Today is a good day!");
} else if (command.equals("Bad")) {
showMessage("Today is a bad day!");
}
}
// Show popup message
private void showMessage(String message) {
JOptionPane.showMessageDialog(null, message,
"Event Handler Message", JOptionPane.INFORMATION_MESSAGE);
}
}
}
So what is different in these? Basically, I've removed your NullPointerException you were getting in DayGui. Any other changes I've made are with the intention than you try and keep your code clutter free, so you really know what is going on in your code.
Hope this helps.

When I run it, both JPanels open, but the JTabbedPane does not. I get
a lot of Unknown Source errors.
Well, based on your code and your import section:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
This lines won't compile (unless DayGUI and OfficeAreaCalculator classes are in the same package than your JTabbedPaneAssignment class):
DayGui pnlDay = new DayGui();
OfficeAreaCalculator pnlOffice = new OfficeAreaCalculator ();
This is the only error I've got trying to compile and run your example. I changed lines below:
tabbedPane.addTab( "DayGui", new JPanel());
tabbedPane.addTab("Office Calculator", new JPanel());
And it worked like a charm.
Update
Based on your recent edit (adding your DayGui class, thank you) you have couple of mistakes in your code.
DayGui : this class extends of JPanel so you need to add your components directly on this class, you don't need this panel:
private JPanel dayPanel;
You need to set the layout manager, buttons and background directly on DayGuiclass, like this:
public DayGui() {
cmdGood = new JButton("Good");
cmdBad = new JButton("Bad");
setLayout(new FlowLayout());
add(cmdGood);
add(cmdBad);
setSize(300, 150);
ButtonsHandler bhandler = new ButtonsHandler();
cmdGood.addActionListener(bhandler);
cmdBad.addActionListener(bhandler);
setBackground(Color.CYAN);
}
JTabbedPaneAssignment : I think you're trying to add panel1 and panel2 as tabs but you use add method instead addTab:
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
tabbedPane.add(panel1,"First panel");
tabbedPane.add(panel2,"Second panel");
Also this line:
tabbedPane.addTab("DayGui", panel1);
Should be:
tabbedPane.addTab("DayGui", pnlDay);
Finally in this line you are adding panel2 for a second time and that's not correct:
tabbedPane.addTab("OfficeAreaCalculator", panel2); //I'd comment this line
If you make suggested changes you'll see something like this (BTW the CYAN color almost made me blind :P):
Hope this be helpful and sorry for the extension.

JFrame inside another JFrame

I have a game of chess.
I have written 3 classes.
1st if for game. (chessboard, pieces, and so on)
And another one is for menu. (buttons like new, open, set time)
Both of them use JFrame.
I would like to put both classes mentioned above into the 3rd class. For example the Game window would be on the left, and the menu on the right.
The third class would also show the whole app by JFrame.
How to do that?

You can't put one JFrame inside another. You have a couple of design choices here. You can change your JFrames to JPanels. This is probably the easiest change. On the other hand, you can look at using Internal Frames instead.

In your case i suggest you to use JInternalFrame which can be added inside Jframe try out this code i hope it will work:
package demo;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
public class Demo {
public static void main(String[] args) {
JFrame jf=new JFrame();
jf.setLayout(null);
jf.setSize(1280, 720);
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JInternalFrame jInternalFrame=new JInternalFrame();
jInternalFrame.setLocation(100, 100);
jInternalFrame.setSize(500, 300);
jInternalFrame.setTitle("Internal frame");
jInternalFrame.setVisible(true);
jInternalFrame.setClosable(true);
jInternalFrame.setResizable(true);
jf.add(jInternalFrame);
jf.repaint();
}
}

You can use JPanels for that. It's easier that way... use a JFrame for the main window and for menu items use a JPanel inside it. Search for tutorials on JPanel usage.

The best thing to do would be to leave the outer frame as it is and change the inner contents to JPanels. When I wrote Chess, I had an outer frame which extended JFrame, and inner panel that extended JPanel on which I placed the board. The board itself was comprised of 64 JButtons.
Given your description, I think this would be a good starting point:
package data_structures;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class Chess extends JFrame implements ActionListener {
private JButton[][] tiles;
public Chess() {
setTitle("Chess");
setSize(500, 500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
setLayout(new BorderLayout());
JPanel board = new JPanel();
board.setLayout(new GridLayout(8, 8));
tiles = new JButton[8][8];
for(int y = 0; y < tiles.length; y++) {
for(int x = 0; x < tiles[y].length; x++) {
tiles[x][y] = new JButton();
tiles[x][y].setActionCommand(x + " " + y);
tiles[x][y].addActionListener(this);
board.add(tiles[x][y]);
}
}
add(board, BorderLayout.CENTER);
JPanel options = new JPanel();
options.setLayout(new GridLayout(1, 3));
JButton newGame = new JButton("New");
newGame.addActionListener(this);
options.add(newGame);
JButton openGame = new JButton("Open");
openGame.addActionListener(this);
options.add(openGame);
JButton setTime = new JButton("Set Time");
setTime.addActionListener(this);
options.add(setTime);
add(options, BorderLayout.SOUTH);
revalidate();
}
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
System.out.println(command);
revalidate();
}
public static void main(String[] args) {
new Chess();
}
}
Also, a word of warning:
Fully implementing the logic of Chess is very difficult, no matter what you do for the graphics.
Hope this helps!

I guess that's what you want to do.
public class OuterFrame extends JFrame {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
OuterFrame outerFrame = new OuterFrame();
outerFrame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public OuterFrame() {
JFrame innerFrame = new JFrame();
innerFrame.setVisible(true);
}
}
You have a MainFrame (OuterFrame), and you create it. But, you create a JFrame inside this MainFrame. That's not a beautiful thing to do, but it's certainly a way of opening a "JFrame inside the other". This will give you two "windows" on the screen. You could create countless JFrames inside the MainFrame.