Develop Reference

JavaFX: ImageView cannot load image that was created by the program itself. Error: java.lang.IllegalArgumentException:

I am attempting to create a program in which the user selects an image from a different folder on their computer and JavaFX copies that image into the project directory for future use. A new folder is created that will store the newly created image file. This is essentially the code for selecting and copying the image into the project directory:
Stage window = (Stage) ap.getScene().getWindow();
FileChooser fileChooser = new FileChooser();
fileChooser.setTitle("Select Image File");
File selectedFile = fileChooser.showOpenDialog(window);
//Creates a new directory for the new calendar that the user wants to create
File file = new File("src/DefaultUser/" + nameField.getText() + "/");
file.mkdir();
//Creates a new file name with logo as the name, but keeping the extension the same
int index = selectedFile.getName().lastIndexOf(".");
String ext = selectedFile.getName().substring(index);
//Stored in newFileName
String newFileName = "logo" + ext;
File newFile = new File(file.getPath() + "/" + newFileName);
//Copies the selected file into the project src folder, with newFileName as the new file name
Files.copy(selectedFile.toPath(), newFile.toPath());
Then the program moves onto a different scene and thus a different controller actually loads the image into an ImageView. I know that the path for the Image works properly but for whatever reason the program cannot find the image file to load it into the ImageView.
Here is essentially the code used for that:
image.setImage(new Image("DefaultUser/" + imagePath));
Don't worry about what imagePath is in this case because I am absolutely positive it paths to the correct location for the newly created image file. This is because if I close the JavaFX program and rerun it, the image loads properly.
At first, I thought it was because it took time for the image to be copied into the project directory but I checked that the file actually existed within the code and it did so this is apparently not the case. I tried using Thread.sleep() to delay the program a bit so that the code would potentially have more time to copy the file but it still threw the same error: java.lang.IllegalArgumentException: Invalid URL: Invalid URL or resource not found
The strangest part about this is that the program works perfectly fine, it's just that I have to restart the JavaFX program for it to be able to detect the image file, even though I know it exists. Is there something weird about JavaFX and creating new files and accessing them within the same program? I am truly lost. Thank you so much in advance for any help and I'm sorry if this doesn't give enough information because I don't want to have to explain the whole project.

Just like haraldK and James_D said in the comments putting stuff in the src folder is generally a bad idea. I solved the issue by moving the folder out into the project directory instead.

How to specify the path correctly to open a file from a sub directory of my project?

I have my project structure like this
--src
--------------resources
--------------saves
I use this subfolder at multiples times like this:
File tempFile = new File("src/saves/" + videoName + ".json");
or sometimes like this :
ImageView icon = new ImageView("resources/edit.png");
and :
File f = new File("src/resources/zelda.mp4");
For some reasons it works for the icon but not for the video/file, when I try I get this error:
Caused by: MediaException: MEDIA_UNAVAILABLE : C:\Users\histackoverflow\IdeaProjects\project2\resources\zelda.mp4 (specified path can't be found)
so I want to know what is wrong in my way of using path ?

#Edit: this works fine for referencing files in IDE. For appropriate file references in jar, follow this: Java Jar file: use resource errors: URI is not hierarchical
I wouldn't recommend typing in the path as a String. A better way of loading files is placing them into recources (you already did that) and call the rescource by class reference and getting URI from it:
InputStream file = new FileInputStream(getClass().getResource("/edit.png").getPath());
Image image = new Image(file);
ImageView icon = new ImageView(image);
File f = new File(getClass().getResource("/zelda.mp4").toURI());
Make sure, that your directory with resources is marked as a resource directory.

Deploying images used in Java Application with the built jar file

After using images for example on a Button, when I build the application creating the .jar file and execute only the file, the images are not there but would only show if I copy the images folder in the same directory as the jar file. Why is that and how can I resolve this if possible?
I am currently using the following code to set the icon/image:
JButton btn = new JButton("Text", "img/icon.png");

The fact that you can use the images when they are stored outside the jar, suggests that you are doing something of the kind:
File image = new File("directory/image.jpg");
InputStream is = new FileInputStream(image);
This reads a file from a directory on the file system, not from the classpath. Now, if you have packaged your image in a "directory" inside your Jar, you must load the image from the classpath.
InputStream is = getClass().getResourceAsStream("/directory/image.jpg");
(note the slash in the path)
Or
InputStream is = getClass().getClassLoader().getResourceAsStream("directory/image.jpg");
(note the absence of the slash in the path)
Your example, as it is now, should not compile. (The second argument of your JButton construtor is an Icon, not a String, java 8). So when you were getting the image from the file system, you were probably doing something else.
With your example, you need to read an image from the inputstream and convert it to an Icon:
try (InputStream is = getClass.getClassLoader().getResourcesAsStream("directory/image.jpg")) {
BufferedImage image = ImageIO.read(is);
return new JButton("Text", new ImageIcon(image));
} catch (IOException exc) {
throw new RuntimeException(exc);
}
That should use the image that is located in "directory" inside your jar. Of course, you need to include the image within your jar, or you will get a NullPointerException on the inputstream is.

I think you need to understand the
ClassLoader:
A typical strategy is to transform the name into a file name and then
read a "class file" of that name from a file system.
So with this you will be able to lead Resources of your project with getResource
public URL getResource(String name)
Finds the resource with the given name. A resource is some data
(images, audio, text, etc) that can be accessed by class code in a way
that is independent of the location of the code.

Unable to locate/open image inside exported jar

I have explored every single solution related to this problem on Stack Overflow, and the solutions I encountered worked only in my IDE (Eclipse Mars), but when exported they all failed.
I have an image file I simply want to load from inside my exported jar.
As you can see from the project layout, Images is a folder directly inside of the project folder CooldownTrackerJava. To refer to it, I've tried a variety of methods.
//My class' name is AddItemDialog
//Method 1
String filePath = File.separator + "Images" + File.separator + "questionMark.png";
InputStream inputStream = AddItemDialog.class.getResourceAsStream(filePath);
BufferedImage img = ImageIO.read(inputStream);
I tried method 1 in a few ways. I tried it with and without the File.separator at the start of the filePath. I understand that the former refers to an absolute path, while the latter is relative. I also tried moving the Images folder inside of the directory where my class files were.
All of these failed giving me a NullPointerException when exported and tested multiple times.
//Method 2
String saveLocation = File.separator + "Images" + File.separator + "questionMark.png";
Image img = Toolkit.getDefaultToolkit().getImage(getClass().getResource(saveLocation));
As per this post I tried the above method however it still did not work.
I've tried many variations aside from the ones mentioned in this post but none of them have been successful when I exported the jar.
Do I need to add the Images folder to my build path? Should I move it to the src folder? Am I missing one obvious step? All suggestions would be highly appreciated. Also here is the layout of the exported jar file.

The solution was a two-part effort. Firstly, I moved my Images folder into the src directory as shown below. Kudos to Matthew.
I then removed File.separator and replaced it with a forward slash/. Thanks to fge.
Do not use File.separator(). Separators for resource paths on the class path is always /. If you use Windows you will therefore always get the wrong result.
I used a variant of method 1 to test it. Both methods will work though.
String saveLocation = "/Images/questionMark.png";
InputStream inputStream = this.getClass().getResourceAsStream(saveLocation);
try {
BufferedImage img = ImageIO.read(inputStream);
} catch (IOException e) {
e.printStackTrace();
}

How to read big bufferedimage

I am reading a 100 MB picture into my app. It works fine inside Eclipse, but not when I export project to a JAR. Then, I get "Can't read input file!"
Since I need to edit it, I used BufferedImage.
private String str = "images/1.png";
BufferedImage imageMap;
//in constructor
imageMap = ImageIO.read(new File(str));
I have tried this, but the project image does not load inside Eclipse:
imageMap = ImageIO.read(this.getClass().getClassLoader().getResource(str));

Check you working directory if the image is loaded from the file system. Then you see if your relative path "images/1.png" is valid. Or you directly check the path of your png
System.out.println(new File("."));
File f = new File("images/1.png");
System.out.println(f.getAbsolutePath());