" Packages can provide a way to offer clients incremental access to upgrades. By introducing new classes in a new package, you can give them the same name as the old classes. For example, if I can upgrade org.junit.Assert in org.junit.newandimproved.Assert, then clients need only change the import statements to be using the new class. Changing imports is less risky and intrusive than changing code. "

― Kent Beck , Implementation Patterns