Lecture 6 - Polymorphism

What is polymorphism?

Enables a single interface (method or type) to represent multiple types. This is achieved through Method Overloading, Method Overriding, Upcasting/Downcasting.

What are the benefits of polymorphism?

Reusability, flexibility and maintainability.

What is method overloading?

Compile-time polymorphism, where o   you use the same method name with different parameters for different constructors (in the same class). Avoid overloading with nearly identical parameter lists.

What is Method overriding?

Run-time polymorphism, where you redefine a superclass method in a subclass, determined at run time through the @Override keyword. This is basically just inheritance!

What is upcasting?

Assigns a subclass object to a superclass reference.

Animal a = new Dog(); //Upcasting
a.makeSound(); //Calls the dog’s version at runtime.

What is downcasting?

Converts superclass reference back to subclass.

Animal a = new Dog();
If (a instanceof Dog) { Dog d = (Dog) a; } //Downcasting

What aspect of abstraction is also polymorphism?

Interfaces, because you are using the same method signature, but promotes loose coupling where components interact via interface, not class.