38. Reorganization of class hierarchies

• Most common reorganizations of a class hierarchy are

  • factoring the common part of two classes into a new class, and

  • splitting a class into two new ones.

• The result is three classes: a base class and two derived classes.

• When should such reorganizations be done? Indicators that such a reorganization is due might be:

  • If commonality between classes is observed, then factor out the common part. Also,

  • common patterns of use,

  • similarity of operations,

  • similarity of implementations.