What is the essence of run-time polymorphism behavior?
With runtime polymorphism based on method overriding, the decision as to which version of a method will be executed is based on the actual type of object whose reference is stored in the reference variable, and not on the type of the reference variable on which the method is invoked. The decisions as to which version of the method to invoke cannot be made at compile time. That decision must be deferred and made at runtime. This is sometimes referred to as late binding.
