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Can I have my entire application in a single JAR file?

I don't quite understand how creation of a Swing application really works.
I have created a simple application that gets a background image from a path.
ImageIcon imageIcon = new ImageIcon("C:\\Java\\ApplicationName\\out\\Resourses\\backGround.jpg");
Image image = imageIcon.getImage(); // Создание картинки из него
Image temp = image.getScaledInstance(500,500,Image.SCALE_SMOOTH);
imageIcon = new ImageIcon(temp);
g2d.drawImage(temp,0,0,null);
It works, so I decided to make a JAR file independent from changes in the Java folder (like deleting this image) and put images in src - images ( package ). I don't know if it is possible though.
I started to get background image like this.
ImageIcon imageIcon = new ImageIcon(this.getClass().getResource("/images/backGround.jpg"));
The program works perfectly in IntelliJ IDEA but if I extract it to JAR file I get a blank background screen. Why is that?
And can I have my entire application including images in a single JAR file? One that is not dependent on other folders?

You can certainly put the image and the code in a single jar file. The image is not loading either because it's not in the jar file, or because it's not at the path /images/backGround.jpg inside the jar.
One helpful thing about jar files that you may not know: they are in .zip format, so you can use any zip tool to see what is inside the jar (temporarily renaming the jar file to .zip might make this easier). IF the image is not there, fix your jar build (you didn't say how you are making it, so not sure what you need to change). If the image is there but under a different path, then fix the jar build to put it in the right place, or change the path you are reading it from.

Yes definitely you can include your entire application into single jar file i.e. Runnable jar file. But i would suggest you not to include your image inside the jar file, instead pass that image path to an Property file and use that property file in your code for image path. So that even if next time you need to change the image you just change the path in your property file and you dont have to export your entire project again.

images not showing up when running JAR

I've spend 5 hours already and have no idea why images are not loaded when running Jar.
Project structure:
Blackjack_Game
- Source Packages
- Images
- blackjack
.... classes...
At project properties I have src - Source Packages folder added by default. Tried to put images directly into the project's folder and removing /Images/, but still no help.
Inside the code I have:
dealer_url = getClass().getResource("/Images/4_of_hearts.jpg");
File img = new File(dealerCardGenerator.dealer_url.getPath());
BufferedImage bufferedImage = ImageIO.read(img);
dealerCardGenerator.imageIcon = new ImageIcon(bufferedImage);
So inside NetBeans IDE everything is OK. Fully working. But after built&clean I see no images, but all actions are done.
Can you please suggest what is wrong? Getting so mad because of this ((((

A jar entry is not a file. java.io.File can only identify a file, not a jar entry. java.net.URL however can identify a jar entry using the jar: scheme, or a file using the file: scheme. That's why Class.getResource() returns a URL not a File.
Two solutions:
use the URL: ImageIO.read(getClass().getResource("whatever"))
ImageIO can also use an already-opened stream, which classloader can provide:
ImageIO.read(getClass().getResourceAsStream("whatever"))
Duplicate of at least #2-4 of the questions autosuggested as related:
Including Images with an executable jar
Loading images in a jar
Getting images from a .jar file

Thank you all for clarifying the problem. I've realized why some functions were not working.
So the solution is to replace URL with ImageIcon:
ImageIcon i2 = new javax.swing.ImageIcon(getClass().getResource("whatever"));
and then just set icon as label icon:
jLabel1.setIcon(i2);
In this way JAR works. Previously, all methods after this icon set operation were not working, as the program was actually stopped, now everything works fine.

Which is the right way to link images and export in Eclipse (Java)?

The problem I'm having right now has to do with how images are linked when exporting the jar. Right now, my program runs on eclipse and the images do work, but when I try to run it from the exported file, the screen goes white. I have the images in a src/res folder and they appear inside the jar just free in the root directory. the code which I use to link the images is this one:
img = ImageIO.read(Thread.currentThread().getContextClassLoader().getResourceAsStream(
"\\bkg.png"));
My question is, how should I write the path so I can export the jar and get the images to work? Or which line of code should I use to make it work?
Thanks in advance,

Use this :
img = ImageIO.read(MyClass.class.getResourceAsStream(path));
Doing this, you have to know that path is a local path starting from the package of MyClass.

My resource does not load - "Input stream must not be null"

I read ~4 Stackoverflow Posts (1, 2) already, and did everything like it was explained there, but I get a NullPointerException while I try to load an Image.
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException: Input stream must not be null
My package structure:
Code where I try to load the image:
Image image = new Image(this.getClass().getResourceAsStream("/regexgolf2/ui/img/edit.png"));
I don't understand why It does not work.

Your images are in a package under the src folder. The class loader does not look there for files. The class loader looks for files in your class path.
In order for getResource to work in your case, you need to put the images in the class path.
I suggest you copy the image files manually to your build folder (under the same path, e.g. out/regexgolf2/ui/images and run your app again.
If it works you can start thinking of ways to get the files to the class path (e.g. copy them as part of the build/packaging process or putting them in another folder which is in the class path).

In the case of a netbeans maven javaFX project, the resource (img folder) must be in the resources folder:
Then you can load the resource, for example:
Image escribir = new Image(getClass().getResourceAsStream("/img/login.png"));

I have similar problem in IntelliJ, all look fine but didn't work. In my case, When I rebuild project, all work correct.

I had the same problem in IntelliJ , I wanted to show Image in ImageView on button click and this was a solution for me, don't use getClass().getResourceAsStream("imagePath");
Image image = new Image(String.valueOf(new File("/images/image3.png")));

You can try:
URL url = ClassLoader.getSystemClassLoader().getResource("img/pic.jpg");
Image imProfile = new Image(url.openStream());
ImageView profileImage = new ImageView(imProfile);

Image not loading in jar file

I am trying to fix this problem. Trying different solutions but nothing works. I am using NetBeans IDE. I created a project with this structure and files:
E:\java\project\ecadpb\src\ecadpb
The image files are in
E:\java\project\ecadpb\src\
I have specified working folder for my project in Netbeans as E:\java\project\ecadpb
I have created my image icons like this
new ImageIcon("device21.png");
In my source file, it works perfectly while running the project in Netbeans but images are not showing up when I build and run my JAR file separately. But the image files are inside the JAR.
I have also tried the answers for the same question asked previously.
URL imageUrl=getClass().getResource("device21.png");
new ImageIcon(imageUrl);
But it doesn't work in my case. I am building a JAR file for the first time. Can anyone help me with this!!

A simple way of doing this will be to add the image in your classpath or a directory in your classpath say img as shown below:
E:\java\project\ecadpb\src\main\java\img\device21.png
And then load your image from this location like this:
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
URL resource = classLoader.getResource("img/device21.png");
ImageIcon icon = new ImageIcon(resource);

Create a source folder called Images (ie if you're using eclipse, right-click your project -> new ->sourceFolder). Call it whatever you want, i called my Images. Put some images in it.
Now i had JLabels where i gave them ImageIcons. Look at the following code.
ImageIcon BPawn;
ImageIcon WPawn;
JLabel Label = new JLabel[8][8] //2D array of labels that gives each spot a position.
public void setPieces(){
//set up pawns in their respective positions.
BPawn = new ImageIcon("Images/BPawn.png", "BPawn");
WPawn = new ImageIcon("Images/WPawn.png", "WPawn");
for(int i=0;i<Label[0].length;i++){
Label[1][i].setIcon(BPawn);
Label[6][i].setIcon(WPawn);
}//end for
}//end setPieces.
There is a lot more in setPieces() method, but this glimpse is how you would reference the images in your source folder when you create an executable jar and want the images to show up.

I think answer could be one these suggestions here

I have used a similar approach,
a) Specify the package path to the image file name.
b) Make sure that the image file is not ommited by your build scripts and that it is present in your jar file.