A cohesive class gives its methods and instance variables one closely related primary responsibility. Its purpose remains clear, and maintenance stays localized because the class has only one reason to change. section 2.3.1 section 4.2.1
Separate automobile responsibilities
A single Automobile class that accelerates, adjusts headlights, changes oil, changes tires, and cleans the car mixes operations, maintenance, and cleaning. Refactor it into Automobile for automobile operations, Garage for maintenance, and CarWash for cleaning; Garage and CarWash receive the Automobile they operate on. section 4.2.1
Book catalogue
Book stores title and author attributes, while Catalogue maintains Book objects, adds entries, and finds matches. Case-insensitive matching treats an empty target attribute as a don't-care, allowing searches such as every book by King. section 2.3.1
