>Java interfaces (as well as C++ interfaces) are more an insurance for polymorphism than multiple inheritance (technically, classes don't inherit anything from interfaces). They are only a contract between programmer and compiler that certain methods will be there.

I think of them as contracts aswell. What is a C++ interface, The Java interface is semantically part of the language. C++ has no such thing. C++ templates are nice, but Java's single base object makes them unnecessary.