My eclipse 4.2 Juno can’t install anything related to Google App Engine Java SDK & Google Web Toolkit. I have seen similar questions & answers. They suggested opening eclipse with –clean argument, running with administrative permissions, installing plugins with administrative permissions etc. I tried all of them & needless to say none of them worked. Whenever I check for “what is already installed” I can see them installed but they don’t appear anywhere.

I am using Android SDK bundle which is Eclipse Juno wrapped with android tools. As long as these plugins/SDK s have compatibility issue with android plugins it shouldn’t matter.
Installed plugins/SDKs looks like
or 
I have tried installing all the above plugins with JUNO. It works. The order of installation for me is –
Juno Java EE –
GPE – GWT and GAE
Android –