Let's look again at loading FXML:
FXMLLoader.load(getClass().getResource("FirstDocument.fxml")); // URL
The load() method's parameter here is a URL to the FXML file during runtime. It usually looks like the following:
jar:file:/path/to/jar/file/FxmlDemo.jar!/demo/FirstDocument.fxml
So, you will almost never set it directly as a String but through the getResource() method. The getResource parameter can be relative to the current class, as in the preceding examples, or absolute to your JAR directory structure, for example:
FXMLLoader.load(getClass().getResource("/demo/FirstDocument.fxml"));
Using absolute paths allows you to store FXML files in a separate folder rather than among the Java code, which is more convenient ...
