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Cannot refer to the non-final local variable display defined in an enclosing scope

This might be a very basic question. But I am stuck at this. The error that I get for the String variable display states:
Cannot refer to the non-final local variable display defined in an enclosing scope.
If I use a final keyword, I get the message:
The final local variable display cannot be assigned, since it is defined in an enclosing slope.*
The code is:
public class Frame {
public static void main(String[] args) {
String display=" ";
Frame ob=new Frame();
JFrame frame=new JFrame("Test");
frame.setBounds(300,100,800,500);
//Container c=frame.getContentPane();
frame.setLayout(null);
final JTextField name=new JTextField();
name.setBounds(500,212,150,20);
JLabel nameLabel=new JLabel("Name: ");
nameLabel.setForeground(Color.WHITE);
nameLabel.setBounds(450,171,100,100);
JTextField ohr=new JTextField();
ohr.setBounds(500,282,150,20);
JLabel ohrID=new JLabel("OHR ID: ");
ohrID.setForeground(Color.WHITE);
ohrID.setBounds(450,241,100,100);
final JButton button=new JButton("Submit");
button.setBounds(530,350,90,20);
frame.add(name);
frame.add(ohr);
frame.add(ohrID);
frame.add(nameLabel);
frame.add(button);
frame.getContentPane().setBackground(Color.DARK_GRAY);
frame.setVisible(true);
button.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
if(e.getSource()==button){
display=name.getText();
JOptionPane.showMessageDialog(null, "Hi "+ display);
System.exit(0);
}
}
});
}
Thanks in advance!

There are multiple issues with your code, and we'll address them right here, right now and solve your problem at the same time.
public class Frame { this particular line has an error, Frame is the name of an AWT class, so it might confuse you or anyone who reads this code later on, give it a more meaningful name and avoid those names that could be confused with other Java packages.
Frame ob=new Frame(); you create an instance of your class and never use it again, why?
frame.setLayout(null); NEVER, please don't use null-layout, Swing has to deal with multiple PLAFs, screen sizes and resolutions, different OS, pixel perfect apps might seem like the easiest way to create complex UIs but later on you'll find that errors like this happen very often.
.setBounds(...) on every component, again, this is due to null-layout but it's better to use Layout managers
final JTextField name=new JTextField(); There's no need to declare any of your components as final, this is due to a poor design of your class, your components should be declared as class members (outside any method including main).
Speaking about main, separate your program into smaller pieces, don't throw everything at main or at the very least create a method that is not static so you can call it after creating an instance of your class (or else later on you'll end up with tons of static variables and that's a poor design of your class once again).
System.exit(0); it will stop the JVM, it's never a good idea to do that, it's better to .dispose() the JFrame and have your JFrame's defaultCloseOperation set to EXIT_ON_CLOSE which will safely dispose your app and then stop the JVM.
display=name.getText();, for this particular case, display could be an inner variable rather than a class member. This will solve your particular question
JOptionPane.showMessageDialog(null, "Hi "+ display); that null should be a reference to your JFrame, this will place your dialog in the middle of that JFrame rather than in the middle of the screen.
You never place your program inside the EDT, see point #2 in this answer.
So, having all the above points in mind, here's an improved version of your code.
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class UsingVariablesInsideActionListenerExample {
//We declare our components here
private JFrame frame;
private JButton button;
private JTextField name;
private JTextField ohr;
private JLabel nameLabel;
private JLabel ohrID;
private JPanel pane;
private JPanel namePane;
private JPanel ohrPane;
public static void main(String[] args) {
SwingUtilities.invokeLater(new UsingVariablesInsideActionListenerExample()::createAndShowGUI); //This is using Java 8 lambdas to place your program in the EDT
}
private void createAndShowGUI() {
frame = new JFrame("Test"); //Create your JFrame
pane = new JPanel();
pane.setLayout(new BoxLayout(pane, BoxLayout.PAGE_AXIS)); //This will make this JPanel to arrange components vertically
namePane = new JPanel(); //By default, JPanels have FlowLayout which will arrange components horizontally
ohrPane = new JPanel();
name = new JTextField(10); //We create a JTextField with 10 columns
nameLabel = new JLabel("Name: ");
nameLabel.setForeground(Color.WHITE);
ohr = new JTextField(10);
ohrID = new JLabel("OHR ID: ");
ohrID.setForeground(Color.WHITE);
button = new JButton("Submit");
//Add the action listener
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == button) {
String display = name.getText(); //The display variable is now an inner variable rather than a class member
JOptionPane.showMessageDialog(frame, "Hi " + display);
frame.dispose(); //We dispose the JFrame and it will be closed after due to EXIT_ON_CLOSE below.
}
}
});
//We add the components to the namePane (horizontally), the order matters
namePane.add(nameLabel);
namePane.add(name);
//Now we add these components to the ohrPane (horizontally again)
ohrPane.add(ohrID);
ohrPane.add(ohr);
//We then add the name and ohr panes to a bigger JPanel (pane, which if you remember will add them vertically) and we add the button at the end
pane.add(namePane);
pane.add(ohrPane);
pane.add(button);
//We make them non opaque (transparent) so that we can see the background color of the JFrame
namePane.setOpaque(false);
ohrPane.setOpaque(false);
pane.setOpaque(false);
frame.add(pane);
frame.getContentPane().setBackground(Color.DARK_GRAY);
frame.pack(); //This will get every component's preferred size and make the JFrame as small as possible where it looks good on every OS, PLAF, screen size and resolution.
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true); //We make the frame visible (always at the very end, when we've added everything to it).
}
}
And this is how it looks like now.
The UI may not be perfectly equal to the one you have, but I'm sure you can play with the different layout managers, and nest various JPanels to get a much better looking UI than mine, or at least a more similar one to the one you had.

Variable used in side an inner class should be effectively final . You can use a string[] of length 1 instead of string to resolve this . Please read bellow post for more details
Difference between final and effectively final
Also check this post for more details
Variable used in lambda expression should be final or effectively final

JComponents only appear after resizing [duplicate]

This question already has answers here:
Java items appear only after the window is resize
(2 answers)
Closed 5 years ago.
I've encountered what I am pretty sure is a glitch, and have not found any way around it. I, at present, have only a simple window that has a text field and a label. When I first run the program, what appears is an empty window, when I resize the window, either by maximizing or just manually resizing a little bit, the components appear, what's going on here?
public class Calculator {
public static void main(String[] args) {
JFrame mainFrame = new JFrame("Calculator");
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.setSize(300,400);
mainFrame.setLocationRelativeTo(null);
mainFrame.setVisible(true);
JPanel mainPanel = new JPanel();
mainFrame.add(mainPanel);
JTextField mainField = new JTextField(20);
mainPanel.add(mainField);
JLabel mainLabel = new JLabel("Orange");
mainPanel.add(mainLabel);
}
}

By default the size of all components is (0, 0), so there is nothing to paint.
Components need to be added to the frame BEFORE the setVisible() method. Then when the frame is made visible the layout manager is invoked and components are given a size/location.

You're adding components to the frame after calling setVisible(true).
This question has already been asked.
Java items appear only after the window is resize

JPanel in JScrollPane not showing [duplicate]

This question already has answers here:
Why is my table not visible when it's in a JScrollPane?
(2 answers)
Closed 8 years ago.
I'm busy making a level designer for a game I'm planning to make in Java. I have a panel for settings, for example the size of the level or what the background will be. You can also select images to put on the other panel, the 'DesignerPanel' and then you should be able to click on that panel to put it in a specific place. I put the DesignerPanel in a JScrollPane to scroll around bigger levels.
The problem is that the JScrollPane doesn't appear and neither does the panel that should be in it. I have found some questions about the scroll bars not appearing, but in my case nothing appears. Well, at least, almost nothing.
You can see really small stripes of the DesignerPanel to the right and below. However, there is no trace of the JScrollPane or the rest of the panel. Resizing or minimizing and unminimizing the screen doesn't make a difference. I would post an image and I think it would surely help, but apparently I need reputation to do that, so sorry about that.
Here's the relevant code I have so far. I have hidden most of the code because it is not important for this error.
package games;
import java.awt.*;
import java.io.*;
import javax.swing.*;
class LevelDesignerScreen extends JFrame
{
private SettingsPanel sp;
private DesignerPanel dp;
private JScrollPane scroller = new JScrollPane();
LevelDesignerScreen()
{
sp = new SettingsPanel(this);
add(sp, BorderLayout.WEST);
dp = new DesignerPanel(sp);
dp.setSize(1000, 1000);
scroller.setPreferredSize(new Dimension(600, 600));
scroller.add(dp);
add(scroller, BorderLayout.CENTER);
}
public static void main(String[] args)
{
new LevelDesignerScreen();
}
}

You should use
scroller = new JScrollPane(dp);
or
scroller.setViewportView(dp);
instead of scroller.add(dp).
And on a more general note: if you are having problems with layout, put prime colored line borders on all involved components to see what takes up space and what doesn't.

GUI Disappearing when I add JComboBox

Alright I'm relatively new to programming and it may be just something simple that I'm missing but the other threads related to this topic the poster didn't give adequate information relative to their issue for others to provide quality answers so I will give it a shot.
public BenchUI(JFrame j){
jf = j;
init();
add(mainPanel);
topPanelButtons();
selectedCustomer();
rentalOptions();
clientListBox();
}
At this point i can point out that everything works perfectly until I add the clientListBox() method. (below)
public void clientListBox(){
clientList = new JComboBox(moo);
clientList.setPreferredSize(new Dimension(460,30));
gbc.gridx = 0;
gbc.gridy = 0;
leftSide.add(clientList,gbc);
}
i can comment it out and get my whole GUI back working perfectly but without a JComboBox.
moo is String [] moo = {"Fish","Goat", "Monkey"};
a dummy string just for testing purposes and initialized at the start.
So any idea why my GUI completely disappears when I place in the clientList?
If anything else is necessary I'll be watching this thread and can provide additional information.
As a side note I keep getting warnings for "Raw Types" but it works without specifiying, could I potentially run into trouble by not specifying my JComboBox?
EDIT:
ok I believe I've duplicated whatever the issue is in this code
import javax.swing.JFrame;
import javax.swing.*;
import java.awt.*;
public class main {
public static void main(String[] args){
JFrame jf = new JFrame();
jf.setExtendedState(JFrame.MAXIMIZED_BOTH);
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setResizable(false);
BenchUI bu = new BenchUI(jf);
jf.add(bu);
}
}
public class BenchUI extends JPanel{
JPanel one;
JFrame jf;
JComboBox<String> clientList;
String[] moo = {"Goat", "Fish", "Donkey"};
public BenchUI(JFrame j){
jf = j;
one = new JPanel(new GridBagLayout());
one.setBackground(Color.blue);
one.setPreferredSize(new Dimension(300,300));
clientList = new JComboBox<String>(moo);
one.add(clientList);
add(one);
}
}
with the clientList stuff commented out I get my silly little blue panel and once it is added I lose the blue panel and the combobox doesnt show up as well...betting on this is a facepalm issue at this point >.<
EDIT: to include the main class.
EDIT: took out the comment marks for the JComboBox constructor and implementer

Your posted sort of sscce-like (not a real SSCCE by the way since we can't run it) code doesn't add any such as the JComboBox to the JPanel and adds no components such as the current JPanel to the JFrame.
public class BenchUI extends JPanel{
JPanel one;
JFrame jf;
JComboBox<String> clientList;
String[] moo = {"Goat", "Fish", "Donkey"};
public BenchUI(JFrame j){
jf = j;
one = new JPanel(new GridBagLayout());
one.setBackground(Color.blue);
one.setPreferredSize(new Dimension(300,300));
//clientList = new JComboBox<String>(moo);
//one.add(clientList);
add(one);
}
}
and so it makes sense that none of the components will show up on any JFrame. You will want to read the Swing tutorials on how to add components to other components (or containers) and how to create and show a JFrame. Have a look at How to Use Swing Components.
Edit
Your latest code now does in fact add the BenchUI JPanel to the JFrame, but still you add no components to the BenchUI JPanel, and in fact you don't even construct your JComboBox but only create a JComboBox variable. Again, I strongly urge you to read the Swing tutorials which I've linked to above as well as the general Java tutorials.
Edit 2
Some general advice:
If you want to add a component to a GUI you must first create the component object. You are declaring your clientList JComboBox, but you never create the object.
Then you must add the component object to a container that eventually will be part of the hierarchy leading to a top level window such as a JFrame, JDialog, JApplet and such. You never add a clientList object to the GUI.
You should add your components to the top level window before calling pack() on the top level window -- which tells all the layout managers to lay out all the components they hold.
You should then call setVisible(true). One problem with your code (other than not creating important components and not adding them to the GUI!) is that you're calling setVisible(true) on your JFrame way too early before adding anything to the GUI.
Read the Swing tutorial, but especially the one on using layout managers and on adding components to a top level window.
Edit 3
OK, now you're creating your JComboBox, but you still are adding all components to your JFrame after setting it visible. Please re-check my 3rd and 4th bullets in the bullet list above.

JFrame not being made at right dimensions

This code, when run, will make a window but not at the specified dimensions. What is wrong with it?
import javax.swing.*;
import java.awt.*;
public class Windowing {
void JFrame(){
JFrame frames = new JFrame("Total recall");
frames.setSize(1000,8000);
frames.setVisible(true);
frames.pack();
//Buttons push = new Buttons();
//((Buttons) push).buttons();
JTextField wager = new JTextField(1);
wager.setSize(100,200);
wager.setVisible(true);
wager.setLocation(100, 200);
frames.add(wager);
//frames.add(push);
}
}

You could remove the call to frames.pack(); it overrides the previously set frame size.
However, what you really want to do is remove the frames.setSize(1000,8000) and move frames.pack() down to the bottom of the method; that will ensure that the frame is big enough to display its contents but not too big to fit on the screen.
If you call pack before adding anything to the frame (like you are doing now), it will make the window extremely small; it's probably appearing near the upper left of your screen, but you won't notice it unless you know where to look.

It looks like you have a number of "opportunity areas" here.
To start, it seems like you set frame size to 1000x8000 because you didn't see any change right?
Secondly you call setVisible on the textField because you didn't see that either.
And finally you're setting the size of the textfield ( I guess because you're seeing it take the whole frame )
The problem here is that you have to invoke pack and setVisible at the end of the construction. Also, you have to learn how to use layout managers and frames.
Swing, is very powerful, but it is a bit hard to grasp at the beginning.
These two links will be helpful:
How to make frames
Using Layout Managers
I've changed your code and the result looks like this:
Here's the modified source code.
import javax.swing.*;
import java.awt.*;
public class Windowing {
public static void main( String [] args ) {
Windowing windowing = new Windowing();
windowing.showFrame();
}
void showFrame(){
JFrame frame = new JFrame("Total recall");
JButton push = new JButton("Push");
JTextField wager = new JTextField(15);
// Panels do have "FlowLayout"
JPanel panel = new JPanel();
panel.add(wager);
panel.add(push);
frame.add( panel );
frame.pack();
frame.setVisible(true);
}
}

Try to use setPreferredSize(Dimension) instead.