Once i also strucked in this problem and i keep remaining surfing the internet to get help everywhere but everything worthless. But after a lot of hardwork, i solved it.
Google app engine doesn’t support JDK 8.
So try to install JDK 7.
And make the changes as follow:
The compiler compliance level should be 1.7
In my case,
finaly i installed Eclipse Luna with JDK 7.
If any problem still arises, comment here. i will try to solve it.