Single-responsibility principle

"A class should only have a single responsibility, that is, only changes to one part of the software's specification should be able to affect the specification of the class."

Open–closed principle

"Objects/entities should be open for extension but closed for modification"

Liskov substitution principle

"q(x)-x of type T-provable then q(y)y of type S & is a subtype of T-also provable"

Interface segregation principle

"A client should never be forced to implement an interface that it doesn't use"

Dependency inversion principle

"Entities must depend on abstractions, not on concretions"

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