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Common Reuse Principle

Design Principles

Classes that aren’t reused together should not be grouped together. A dependency upon a package is a dependency upon everything within the package. When a package changes, and its release number is bumped, all clients of that package must verify that they work with the new package -- even if nothing they used within the package actually changed. We frequently experience this when our OS vendor releases a new operating system. We have to upgrade sooner or later, because the vendor will not support the old version forever. So even though nothing of interest to us changed in the new release, we must go through the effort of upgrading and revalidating. The same can happen with packages if classes that are not used together are grouped together. Changes to a class that I don’t care about will still force a new release of the package, and still cause me to go through the effort of upgrading and revalidating.