Single Responsibility Principle

Open Closed Principle

Liskov Substitution Principle

Interface Segregation Principle

Class Interactions

three package principles about package cohesion

SRP / The Single Responsibility Principle  says:
All classes need to change for a reason of enhancements..(future versions/new requirements)
SRP here talks about having more than one reasons for change.-
This can cause problems with code maintainability.

(responsibility = “a reason for change.” )
If you can think of more than one motive for modify / change a class, then
that class has more than one responsibility.
 
There should never be more than one reason for a class to change.