Dealing with a Circular Dependency

I wonder if someone can advise on any good ways to break a circular dependency between 2 classes in Java.FindBugs proposes the use of interfaces so i wonder if someone has any good experie开发者_Python百科nce with this type of problem.

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Circular dependencies aren't always to be avoided. I'd avoid them in the large, but keeps in small tight corners of a system. In the large, i.e if data access layer and the representation layer of J2EE app circular dependent, I'd say that is a bad thing, because it means that everything has to be compiled in one go and testing is nightmare. But, it's no problem if a list data-structure and its iterator type are circular dependend.

As Findbugs suggests use interfaces to break a circular dependency. I.e introduce a interface for at least one type of the circle and make the other classes use the interface everywhere. Do you need example code?

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Suggest reading about the dependency inversion principle, e.g. What is the Dependency Inversion Principle and why is it important? or http://en.wikipedia.org/wiki/Dependency_inversion_principle

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There's a blog post here on how Restructure101 was used to remove cyclic dependencies, "tangles", from Junit and a presentation from the Lausanne JUG on how it was used to remove tangles from Icefaces.

As for the debate on whether cyclic dependencies are bad, I suggest reading Uncle Bob's Solid Principles.

Disclaimer: I work for Headway Software the developers of Restructure101.