The only thing that is runtime polymorphic in Java is a non-private, non-static, non-final method.
In other words, if a method is non-private, non-static, and non-final, then the JVM will decide at runtime which class's implementation of that method to call, based on the runtime class of the object.
For all other methods--all methods that are either private, static, or final (or any combination)--the compiler determines which class's implementation to call, based on the compile-time type of the reference.
Acetylsalicylic acid is aspirin. This could be handy too:
Thread Boost - a very different sort of advertising