Pull Up Method
ProblemYour subclasses have methods that perform similar work.
SolutionMake the methods identical and then move them to the relevant superclass.
Subclasses grew and developed independently of one another, causing identical (or nearly identical) fields and methods.
Gets rid of duplicate code. If you need to make changes to a method, it's better to do so in a single place than have to search for all duplicates of the method in subclasses.
This refactoring technique can also be used if, for some reason, a subclass redefines a superclass method but performs what is essentially the same work.
How to Refactor
Investigate similar methods in superclasses. If they are not identical, format them to match each other.
If methods use a different set of parameters, put the parameters in the form that you want to see in the superclass.
Copy the method to the superclass. Here you may find that the method code uses fields and methods that exist only in subclasses and therefore are not available in the superclass. To solve this, you can:
- For fields: use either Pull Up Field or Self-Encapsulate Field to create getters and setters in subclasses; then declare these getters abstractly in the superclass.
- For methods: use either Pull Up Method or declare abstract methods for them in the superclass (note that your class will become abstract if it was not previously).
Remove the methods from the subclasses.
Check the locations in which the method is called. In some places you may be able to replace use of a subclass with the superclass.