The Syntax and Terminologies

The terminologies

A new class is created based on an existing class in Inheritance, hence we use the terminology below for the new class and the existing class:

• SuperClass (Parent Class or Base Class): This class allows the re-use of its non-private members in another class.
• SubClass (Child Class or Derived Class): This class is the one that inherits from the superclass.

Note: A child class has all non-private characteristics of the parent class.

What does a child class have?

An object of the child class can use:

• All non-private members defined in the child class.
• All non-private members defined in the parent class.

Note: Some classes cannot be inherited. Such classes are defined with the keyword, final. An example of such a class is the built-in Integer class - this class cannot have derived classes.

The extends Keyword

In Java, we have to use the keyword extends to implement inheritance:

SubClass extends SuperClass{
//contents of SubClass
}

Let’s take an example of a Vehicle class as a base class and implement a Car class that will extend from this Vehicle class. As a Car IS A, Vehicle the implementation of inheritance relation between these classes will stand valid.