Smell Data Clumps

Data items that hang around together in lots of places: fields in a couple of classes, parameters in many method signatures. Bunches of data that hang around together really ought to be made into their own object.

• Same three or four data items appear together repeatedly
• Fields in multiple classes that are always used together
• Parameters that always appear together in method signatures

Martin Fowler — Refactoring: Improving the Design of Existing Code, 1st Edition (1999)