how to edit `.class` file in Maven dependency in Eclipse

Question

Ok, so I have my Java projects, and under the Maven dependency project folder on the project explorer, I encounter a jar folder, and in it there is a .cla

Answer 1

Class files are compiled binaries poised to be part of executable programs.

To modify them is an art in modifying compiled source code. You probably don't want to do that. If you want to generate a replacement, download the whole project and recompile it.

You may be obligated to do certain other things under such an action, by law you must abide by the licensing of the software, and recompiling and redistributing (which is what you'll be doing if you must recompile) often puts much heavier burdens on the developer than just "using" (depending on the licensing).