SOLID - OOP Principles to Programming

Principles to program by ->

http://en.wikipedia.org/wiki/SOLID_(object-oriented_design)

S SRP:

Single responsibility principle

An object should have only a single responsibility.

O OCP:

Open/closed principle

“Software entities … should be open for extension, but closed for modification”.

L LSP:

Liskov substitution principle

“Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program”. See also design by contract.

I ISP:

Interface segregation principle

“Many client-specific interfaces are better than one general-purpose interface.”

D DIP:

Dependency inversion principle

One should “Depend upon Abstractions. Do not depend upon concretions.”
Dependency injection is one method of following this principle.