Resolve issue where Java files cannot be selected separately

[2017398956]

See #2590

[vmishenev]

Thank you for contributing.
To fix this properly, i think, it is better to:

1. Fix a typo here. java should be instead of .java.
2. Then needed files will be in sourceRoots. And a function of sourceRoots processing should be changed a little bit.
3. Can you add a test like this?

[2017398956]

Thank you for contributing. To fix this properly, i think, it is better to:

1. Fix a typo here. java should be instead of .java.
2. Then needed files will be in sourceRoots. And a function of sourceRoots processing should be changed a little bit.
3. Can you add a test like this?

@vmishenev
Yes, after insteading .java with java it works well and I had commit a new pr : #2604