Change Preventers

These smells mean that if you need to change something in one place in your code, you have to make many changes in other places too.

Shotgun Surgery

Making any modifications requires that you make many small changes to many different classes. A single responsibility has been split up among a large number of classes.

Treatment

• Move Method and Move Field

• Inline Class

Divergent Change

You find yourself having to change many unrelated methods when you make changes to a class.

Treatment

• Extract Class

• Extract Superclass and Extract Subclass

Parallel Inheritance Hierarchies

Whenever you create a subclass for a class, you find yourself needing to create a subclass for another class.

Treatment

First, make instances of one hierarchy refer to instances of another hierarchy.

Then, remove the hierarchy in the referred class, by using Move Method and Move Field.