Recently I've added a .java file to my Processing Project (its called GClip.java from a library which is called G4P). That .java file helps to copy stuff to the clipboard. I read that on a forum, however directly after I created a new Tab and imported the content from the .java file it gave me that message:
sketch_190108b contains .java tabs. Some editor features (like completion and error checking) will be disabled.
Now I can't see errors and stuff. How can I turn it back on? I've already tried turning it on in the preferences tab but it didn't work... Any help please?
My guess is this is because the error checking comes from the Processing preprocessor, which turns Processing code into Java code. If you're using a .java file, then the prepocessor is skipped, so it can't do its error checking.
If you want to be sure, you could search for the message in the Processing source code here.
You might consider using a Java IDE like Eclipse or Intellij if this is important to you.
Also, please make sure you're following the G4P copyright license when you copy its code.