Common Code Smell

• Duplicated code: identical or very similar code exists in more than one location.
• Long method: a method, function, or procedure that has grown too large.
• Large class: a class that has grown too large. See God object.
• Too many parameters: a long list of parameters in a procedure or function make readability and code quality worse.
• Feature envy: a class that uses methods of another class excessively.
• Inappropriate intimacy: a class that has dependencies on implementation details of another class.
• Refused bequest: a class that overrides a method of a base class in such a way that the contract of the base class is not honored by the derived class. See Liskov substitution principle.
• Lazy class / Freeloader: a class that does too little.
• Contrived complexity: forced usage of overly complicated design patterns where simpler design would suffice.
• Excessively long identifiers: in particular, the use of naming conventions to provide disambiguation that should be implicit in the software architecture.
• Excessively short identifiers: the name of a variable should reflect its function unless it's obvious.
• Excessive use of literals: these should be coded as named constants, to improve readability and to avoid programming errors. Additionally, literals can and should be externalized into resource files/scripts where possible, to facilitate localization of software if it is intended to be deployed in different regions.