Java Inheritance

  • Inheritance is the process of inheriting the attributes (data member) and behaviour (methods) of an existing class into a new class.
  • The new class which inherits all characteristics of the existing class is called as Sub class.
  • The existing class which is being inherited is called as SuperClass.
  • Inheritance can be achieved by adding ‘extends’ keyword near the sub class name and then followed by the superclass (class which has to be inherited).

Example:

  • The subclass can access the attributes and behaviour of the superclass in addition to its own attributes and behaviour.

Consider a class vehicle which has 3 subclasses – car, ship, flight. Inheritance The methods start(), stop(), parking() are common to all the vehicles and hence they are added in the vehicle class. The car class contains driving() method and the methods start(), stop(), parking() which are inherited from the vehicle class.

Similarly the classes ship and flight have the methods specific to them in addition to the methods inherited from the vehicle class.

  • A class cannot extend more than one class. Multiple inheritance is not allowed in Java unlike in C++. But one super class can have multiple sub class.
Class A extends B, C // not allowed


Class M extends A
Class N extends A
Class O extends A    // class A has 3 subclasses M, N, O

Multi level Inheritance:

A subclass can be inherited by another class.

Example:

Member Access in Inheritance:

A subclass can access all the members of the superclass except those which are declared as private.

Example:

 






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