Inheritance in JAVA

Inheritance

The process by which one class acquires the properties and functionalities of another class is called. Inheritance provides the idea of reusability of code and each sub class defines only those features that are unique to it, rest of the features can be inherited from the parent class.

1. Inheritance is a process of defining a new class based on an existing class by extending its common data members and methods.
2. Inheritance allows us to reuse of code, it improves reusability in your java application.
3. The parent class is called the base class or superclass. The child class that extends the base class is called the derived class or subclass or child class.

Note: The biggest advantage of Inheritance is that the code in base class need not be rewritten in the child class.

The variables and methods of the base class can be used in the child class as well.

To inherit a class we use extends keyword. Here class A is child class and class B is parent class.

class A extends B
{
}

Types Of Inheritance

Single Inheritance: refers to a child and parent class relationship where a class extends another class. Multilevel inheritance: refers to a child and parent class relationship where a class extends the child class. For example, class A extends class B and class B extends class C. Hierarchical inheritance: refers to a child and parent class relationship where more than one classes extend the same class. For example, class B extends class A and class C extends class A. Multiple Inheritance refers to the concept of one class extending more than one classes, which means a child class has two parent classes. Java doesn’t support multiple inheritances.

Java doesn’t allow multiple inheritance to avoid the ambiguity caused by it

 

Example

In this example, we have a parent class Teacher and a child class MathTeacher. In the MathTeacherclass we need not to write the same code which is already present in the present class. Here we have college name, designation and does() method that is common for all the teachers, thus MathTeacher class does not need to write this code, the common data members and methods can inherited from the Teacher class.

class Teacher {
  String designation = "Teacher";
  String college = "Beginnersbook";
  void does(){
System.out.println("Teaching");
  }
}
public class MathTeacher extends Teacher{
  String mainSubject = "Maths";
  public static void main(String args[]){
     MathTeacher obj = new MathTeacher();
     System.out.println(obj.college);
     System.out.println(obj.designation);
     System.out.println(obj.mainSubject);
     obj.does();
  }
}

Output:

Beginnersbook
Teacher
Maths
Teaching