How to change the code of a existing library imported for my project in Eclipse?

My problem is with the physics-body-editor from aurelienribon exactly as reported here:

https://code.google.com/p/box2d-editor/issues/detail?id=25

Now there’s a solution at the bottom of that page, but it only provides the enhance source for BodyEditorLoader.java… link

How do I use that code in my project? I’m doing my project in Eclipse and bodyeditor-loader.jar is imported for my project.