Common closure principle

The Common closure principle is concerned with program maintainability. It states:

The classes in a package should be closed together against the same kind of changes. A change that affects a package affects all the classes in that package. ifacethoughts.net

This means: "The classes that tend to be reused together belong in the same package",Robert Cecil Martin 1996b

Although most design principles advocate loose-coupling between classes, sometimes it is unavoidable. This may be because of a consequence of the design, or a deliberate action such as performance tuning. In these cases, these classes should be packaged together, so a change only effects the classes in that package. This makes updating the system easier, as only the new package needs to be distributed. The Law of Demeter is a useful way to find out which classes know other's structure, and thus should probably be in the same package.

See also

• Law of Demeter
• Common reuse principle