What is the main difference between Inheritance and Polymorphism?

by

Inheritance is when a ‘class’ derives from an existing ‘class’. So if you have a Person class, then you have a Student class that extends Person, Student inherits all the things that Person has. There are some details around the access modifiers you put on the fields/methods in Person, but that’s the basic idea. For example, if you have a private field on Person, Student won’t see it because its private, and private fields are not visible to subclasses.

Polymorphism deals with how the program decides which methods it should use, depending on what type of thing it has. If you have a Person, which has a read method, and you have a Student which extends Person, which has its own implementation of read, which method gets called is determined for you by the runtime, depending if you have a Person or a Student. It gets a bit tricky, but if you do something like

Person p = new Student();
p.read();

the read method on Student gets called. Thats the polymorphism in action. You can do that assignment because a Student is a Person, but the runtime is smart enough to know that the actual type of p is Student.

Note that details differ among languages. You can do inheritance in javascript for example, but its completely different than the way it works in Java.

More Related Contents:

  1. Is polymorphism possible without inheritance?
  2. How do I correctly implement this code segment without getting a logic error? [closed]
  3. Is List a subclass of List? Why are Java generics not implicitly polymorphic?
  4. What’s wrong with overridable method calls in constructors?
  5. Polymorphism vs Overriding vs Overloading
  6. Difference between Inheritance and Composition
  7. Extends JFrame vs. creating it inside the program
  8. Do subclasses inherit private fields?
  9. Why is there no multiple inheritance in Java, but implementing multiple interfaces is allowed?
  10. What is an interface in Java?
  11. Why to use Interfaces, Multiple Inheritance vs Interfaces, Benefits of Interfaces?
  12. Java : If A extends B and B extends Object, is that multiple inheritance
  13. What is the difference between dynamic and static polymorphism in Java?
  14. How should I have explained the difference between an Interface and an Abstract class?
  15. Why do we assign a parent reference to the child object in Java?
  16. Overloading in Java and multiple dispatch
  17. Superclass reference not able to call subclass method in Java
  18. How can a derived class invoke private method of base class?
  19. Why use inheritance at all? [closed]
  20. Hiding Fields in Java Inheritance
  21. When do I have to use interfaces instead of abstract classes? [duplicate]
  22. Static Binding and Dynamic Binding
  23. Why we should not use protected static in java
  24. Difference Between Object Type and Reference Type
  25. In Java, how do I call a base class’s method from the overriding method in a derived class?
  26. Access subclass fields from a base class in Java
  27. Why are constructors not inherited in java?
  28. Avoiding parallel inheritance hierarchies
  29. Anonymous vs named inner classes? – best practices?
  30. Why are class static methods inherited but not interface static methods?

Leave a Comment