Are utility classes evil?

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I saw this question: If a "Utilities" class is evil, where do I put my generic code?

And I thought, why are utility classes evil?

Let’s say I have a domain model that is dozens of classes deep. I need to be able to xml-ify instances. Do I make a toXml method on the parent? Do I make a MyDomainXmlUtility.toXml helper class? This is a case where the business need spans the entire domain model -- does it really belong as an instance method? What about if there are a bunch of auxiliary methods on the XML functionality of the application?

software-design design-patterns
14 Answers

Utility classes are not always evil. But they should only contain the methods that are common across a wide range of functionality. If there are methods that are only usable among a limited number of classes, consider creating a abstract class as a common parent and put the methods in it.

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