INHERITANCE, POLYMORPHISM AND INTERFACES

• ·       enables the use of existing class to define a new class.

  INHERITANCE
• ·       It is also known as subclass, child class, and descendant class.

  DERIVED CLASS
• A derived class is defined by adding instance variables and methods to an existing class.
• The existing class that the derived class is built upon is called the base class
• ·       It is also called superclass, parent class, and ancestor class.

  BASE CLASS
• ·       If a derived class defines a method with the same name, the same number and types of parameters, and the same return type as a method in the base class, the definition in the derived class is said to override the definition in the base class.
• A derived class has its own constructors
• ·       A derived class has its own constructors. It does not inherit any constructors from the base class.
• ·       is the ability of an object to take on many forms.

  Polymorphism allows you to make changes in the method definition

  POLYMORPHISM
• ·       allows you to make changes in the method definition for the derived classes and have those changes apply to the methods written in the base class.

  polymorphism
• ·       allows many meanings to be associated to one method name.

  dynamic binding
• is used to specify methods that a class must implement. It contains headings for a number of public methods.

  interface
• ·       should include comments that describe the methods.

  interface
• cannot be instantiated but can be subclassed


  abstract class
• is a method that is declared as abstract and does not have an implementation. This is written without braces, followed by a semicolon


  abstract method
• ·       They both cannot be instantiated and may contain a mix of methods declared with or without an implementation.

  abstract and interface