Single Responsibility Principle

• A class should have one, and only one, reason to change.
• Each class only does one thing and every class or module only has responsibility for one part of the software’s functionality
• More simply, each class should solve only one problem.

Open-Closed Principle

• You should be able to extend a class’s behavior without modifying it
• Open for extension, Closed for modification.
• Open for extension, meaning that the class’s behavior can be extended.
• Closed for modification, meaning that the source code is set and cannot be changed.

Liskov Substitution Principle

• Every derived class should be substitutable for its parent class
• It says when we refer a child class object using the datatype of parent class, there should not be any unexpected behaviour.

Interface Segregation Principle

• Make fine grained interfaces that are client-specific. Clients should not be forced to implement interfaces they do not use.

Dependency Inversion Principle

• Depend on abstractions, not on concretions
• High level modules should not depend upon low level modules. Both should depend on abstractions.
• Abstractions should not depend on details. Details should depend upon abstractions.

NOTE:

To understand the problem first read the files of inefficient folder then you will find the solution in efficient folder where particular principle is used to solve that problem.

Try to read the files of inefficient and efficient folder in sequential order.