Inheritance provides a way to create a new class from an existing class. The new class is a specialized version of the existing class such that it inherits all the non-private fields (variables) and methods of the existing class. The existing class is used as a starting point or as a base to create the new class.

The IS A Relationship

After reading the above definition, the next question that comes to mind is this: when do we use inheritance? Wherever we come across an IS A relationship between objects, we can use inheritance.

Inheritance provides an object with the ability to acquire the fields and methods of another class, called base class. Inheritance provides reusability of code and can be used to add additional features to an existing class, without modifying it.

Sample class Mammal is shown below which has a constructor.Mammal Class 

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public class Mammal{  

 public Mammal()

 {

   System.out.println("Mammal created"); 

 }

}

Man class extends Mammal which has a default constructor. The sample code is shown below.Man class

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public class Man extends Mammal{ 

 public Man()

 {  

   System.out.println("Man is created");  

 }  

}

Inheritance is tested by creating an instance of Man using default constructor. The sample code is shown to demonstrate the inheritance.TestInheritance Class

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public class TestInheritance{

public static void main(String args[])

{  

   Man man = new Man();  

 }  

}