In this note we mainly focus on JAVA but many of these concepts can be applied to other programming languages as well

Inheritance

Inheritance is the representation of arbitrary IS-A Relationships which is also known as a parent-relationship. Inheritance is what enables a new ( Child Class ) mechanism/class/object to acquire the properties and behaviour of another object ( Parent Class).

Key Concepts

• Child Class/Sub Class: Also known as derived extended or child class
• Parent Class/Super Class: Also known as the based class

Purpose of Inheritance

1. Code Reusability: Inheritance allows the reuse of the parent class code in the child class, reducing redundancy and enabling the extension of functionalities without modifying the existing code.
2. Extensibility: New features and behavior can be added to the child class without affecting the parent class. This means the base code can remain intact while the child class can implement or override new functionality.
3. Maintainability: Since common code is centralized in the parent class, changes only need to be made in one place, making it easier to maintain and update code across different child classes.
4. Method Overriding: The child class can change the behavior of methods inherited from the parent class. This is useful when the child class needs to modify or extend the functionality defined in the parent class.

Advantages and Disadvantages

• Code reusability is

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Types of Inheritance

There are various types of inheritance we can implement. These types arise due to ?

Single Inheritance

When there is a single parent the inheritance is called single Inheritance.

classDiagram
    class Parent {
        +methodA()
    }
    class Child {
        +methodB()
    }

    Parent <|-- Child

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Multilevel Inheritance

When the class is derived from a class that is already a child class of some other parent class this entire inheritance can be called as multilevel inheritance.

classDiagram
    class Grandparent {
        +methodA()
    }
    class Parent {
        +methodB()
    }
    class Child {
        +methodC()
    }

    Grandparent <|-- Parent
    Parent <|-- Child

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Hierarchical Inheritance

When a class is parent to two other classes the relationship can be called as Hierarchical Inheritance

classDiagram
    class Parent {
        +methodA()
    }
    class Child1 {
        +methodB()
    }
    class Child2 {
        +methodC()
    }

    Parent <|-- Child1
    Parent <|-- Child2

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Multiple Inheritance

When a child class inherits the properties of two or more different parent classes it is called as multiple Inheritance. The java programming language does not support multiple inheritance. But it can still be achieved using Interfaces.

classDiagram
    class Parent1 {
        +methodA()
    }
    class Parent2 {
        +methodB()
    }
    class Child {
        +methodC()
    }

    Child <|-- Parent1
    Child <|-- Parent2

---

Hybrid Inheritance

classDiagram
    class Parent1 {
        +methodA()
    }
    class Parent2 {
        +methodB()
    }
    class Child {
        +methodC()
    }

    Child <|-- Parent1
    Child <|-- Parent2

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UML of a Inheritance

In this example the shape class is a parent which exhibits Hierarchical Inheritance as the Rectangle and the Circle inherits the properties of the shape.

classDiagram
    class Shape {
        +double area
        +getArea() double
    }

    class Rectangle {
        +double length
        +double width
        +getArea() double
    }

    class Circle {
        +double radius
        +Circle(double r)
        +getArea() double
    }

    Shape <|-- Rectangle
    Shape <|-- Circle

Example of Inheritance

Employee Programmer

class Employee{
	float salary=4000;
}
class Programmer extends Employee{
	int bonus=10000;
	public static void main(String args[]){
		Programmer P = new Programmer();
		System.out.println("The salary of the programmer is: "+p.salary);
		System.out.println("The bonus of the programmer is: "+p.bonus);
	}
}

Programmers Salary is : 4000
Programmers Bonus is : 10000

The mermaid diagram is as follows:

classDiagram
    class Employee {
        +float salary
    }

    class Programmer {
        +int bonus
    }

    Employee <|-- Programmer

References

Information

• date: 2025.02.27
• time: 10:14