My current experience interviewing candidates for several Java development positions tells me that people with strong Java but little or no C++ cannot explain multiple inheritance except to say by rote "Java doesn't have it but instead you use interfaces." But they don't know what it *is*.
Similarly their exposure to templates and operator overload may be lacking. OTOH candidates strong in C++ but not Java may not recognize interfaces by that name.
I suggest instead questions like "Describe an is-a and a has-a a relationship, and give an example of each?" and "Tell me about a book about OOD or OOP that you've used recently?"
See Interview answers for OOP programmers for a bit of help.