Polymorphism is useful any time that the software can't be told at compile time exactly what everything is going to be at runtime, or when you need a container to be able to hold a heterogeneous assortment of things that all implement a common interface.

Why do we use runtime polymorphism in Java?

To simply put, polymorphism in java allows us to perform the same action in many different ways. Any Java object that can pass more than one IS-A test is considered to be polymorphic and in java, all the java objects are polymorphic as it has passed the IS-A test for their own type and for the class Object.

What is the use of dynamic polymorphism in Java?

Dynamic method dispatch allow Java to support overriding of methods which is central for run-time polymorphism. It allows a class to specify methods that will be common to all of its derivatives, while allowing subclasses to define the specific implementation of some or all of those methods.