Welcome to the forum. Very glad you are enjoying Processing and found the materials helpful.
Please don’t be rude to volunteers who try to help you, even if they could not solve your problem. Please also note that not all forum members speak English as a first language–misunderstandings are easy, especially tone.
Regarding your questions:
- p5.js is a JavaScript library.
- Processing (Java mode) is either:
- written in the processing dialect and transpiled to Java 8, or
- imported as a Java library into a Java project, and written in Java
If you want a native Processing (Java) IDE, use PDE, as kll suggested–it sounds like you are already using it, although I couldn’t tell from your initial post. Many new p5.js users skip PDE and use the online web editor or Brackets.
If you want to use one of the editors you are familiar with, first install PDE, then install a package for that editor.
- Sunsetting Atom - The GitHub Blog
- GitHub - b-g/processing-sublime: A Sublime Text package for the programming language Processing
- GitHub - AvinZarlez/processing-vscode: A Visual Studio Code extension for the programming language Processing
These generally access PDE via the command line to do sketch compiling and launching–see for example the Atom installation instructions. Notice that, because Processing is a transpiled dialect, the syntax highlighting / code hinting / etc. is usually not as robust outside PDE (as kll mentioned).
If instead you want to write Processing (Java) sketches in Java, then you should use Eclipse, IntelliJ, or NetBeans – a full Java IDE. To get started, see for example the tutorial: https://processing.org/tutorials/eclipse/. This is more ambitious, but there are certain things you can only do in this way – in particular, authoring PDE contributed libraries or tools.
Hope this was helpful.