GUI Designer Output Options
IntelliJ IDEA's GUI Designer provides two options for the output:
Runtime classes that are generated when you compile the project to which they pertain. In this case, the intermediate step of Java source code is bypassed. Optionally, the compiled classes can be written to the compiler output directory configured for the project.
Java source code. In that case, all code for the UI components is generated to the class to which each form is bound.
Refer to the GUI Designer dialog for the detailed description of options.