In contrast to C# Java supports nested interfaces.
Currently a nested interface "ParentInterface.NestedInterface" is put into a separate class called "ParentInterface_Constants" which makes the name of the NestedInterface to ParentInterface_Constants.NestedInterface. The reason for this are translation runtime performance issues.
A more intuitive and readable but translation time consuming approach would be to put nested interfaces at "top level". The example from above could be translated to something like "ParentInterface_NestedInterface".
This functionality could be optional.
This issue has been discussed here:
http://sourceforge.net/forum/message.php?msg_id=4815238