5 SOLID Principles of Object-oriented Design
S (Single-responsiblity principle)
One class should have one and only one responsibility
O (Open-closed principle)
Objects or entities should be open for extension, but closed for modification.
L (Liskov substitution principle)
Derived types must be completely substitutable for their base types.
I (Interface segregation principle)
Objects or entities should be open for extension, but closed for modification.
D (Dependency Inversion Principle)
Entities must depend on abstractions not on concretions.