I cant import a .Java entity model into the Resources Tab!!

I had a similar problem, for me it was because the internal name had a space in it. Go back to the model creator, click on file, and click edit, you should see the internal name that you set initially. Make it match the file name and make sure it doesn't have invalid characters like spaces or periods. Another issue that might be causing it would be that multiple parts are named the same things or the parts may have invalid names. you may have two "cube3"'s for example, just rename the second one to "cube35" or something (don't use . because that will mess it up), and again, avoid invalid characters.