Solid Principles

Benefits:

1. Better Code.
2. Avoid Duplicate Code.
3. Easy to maintain and understand.
4. Reduce complexity.\

S (Single Responsibility Principal): A class should have only one reason to change.
O (Open Close Principal) - Open for extension but closed for modification.
L (Liskov's Substitution principle) - If Class B is subtype of Class A, then we should be able to replace object of A with B without breaking the behaviour of the program.
I (Interface Segmented Principle) - Interfaces should be such, that client should not implement unnecessary methods that they do not need.
D (Dependency Inversion Principle) -Class should depend on interfaces rather than concrete classes.

Design Patterns

1. Strategy Pattern
2. Observer Pattern
3. Decorator Pattern