Parallel Inheritance Hierarchies.
Whenever you create a subclass for a class, you find yourself needing to create a subclass for another class.
##Signs and Symptoms
Whenever you create a subclass for a class, you find yourself needing to create a subclass for another class.
abstract class Engine {}
class CarEngine extends Engine {}
class TruckEngine extends Engine {}
abstract class EngineView {}
class CarEngineView extends EngineView {}
class TruckEngineView extends EngineView {}
// adding BusEngine also forces you to add BusEngineView##Reasons for the Problem
All was well as long as the hierarchy stayed small. But with new classes being added, making changes has become harder and harder.
##Treatment
Refactor with
##Payoff
-
Reduces code duplication.
-
Can improve organization of code.
