OOD Principles

Class Design Principles

(SRP) The Single Responsibility Principle

A class should have only one reason to change.

(OCP) The Open-Closed Principle

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

(LSP) The Liskov Substitution Principle

Subtypes must be substitutable for their base types.

(DIP) The Dependency Inversion Principle

Abstractions should not depend upon details. Details should depend upon abstractions.

(ISP) The Interface Segregation Principle

Clients should not be forced to depend upon methods that they do not use. Interfaces belong to clients, not to hierarchies.

Principles of Package Cohesion

(REP) The Reuse/Release Equivalency Principle

The granule of reuse is the granule of release.

(CCP) The Common Closure Principle

The classes in a package should be closed together against the same kinds of changes. A change that affects a closed package affects all the classes in that package and no other packages.

(CRP) The Common Reuse Principle

The classes in a package are reused together. If you reuse one of the classes in the package, you reuse them all.

Principles of Package Coupling

(ADP) The Acyclic Dependencies Principle

Allow no cycles in the package dependency graph.

(SDP) The Stable Dependencies Principle

Depend in the direction of stability.

(SAP) The Stable Abstraction Principle

A package should be as abstract as it is stable.