Java complexity metric

Structure101 defines a software complexity metric called XS.  The principal of XS is very simple, but if you keep your XS close to zero, your structure will be considerably simpler (easier to develop, modify, extend, test, reuse, deploy, etc.) than the vast majority of code-bases in the world. 

A unique characteristic of the XS metric is that it can be applied to every item at every level of the hierarchy.  An XS value of 0 is good - it means that the code is not excessively complex (has not exceeded the set limit).

XS considers only two structural measures - "Fat" and "Tangle". 

Fat is the degree to which an item exceeds a size threshold and is applied at every level of the hierarchy.  Fat is measured as Cyclomatic Complexity at the method level, and the analogous measure of the number of edges in the dependency graph is used at all other levels.

Tangle is the degree to which package dependencies are cyclic and is applied only at the design level (i.e. to the contents of high-level packages).  Tangle is measured as the number of "wrong", or upward, dependencies as a percentage of all dependencies on a dependency graph. The Tangle metric is only measured at the package level where it does the most damage (see Bob Martin's Acyclic Dependency Principle (ADP))

Any excessive Fat and Tangle is multiplied by the amount of code in the item to give the XS value for that item.  In this way, problems higher in the hierarchy are "awarded" a higher XS value.  This is important because higher-level problems (such as architectural tangles) tend to cause more chaos that lower-level problems (however widespread low-level problems, such as high method CC, can add up to as big a problem as a tangle at the top level).  Relating XS to the amount of code also allows us to indicate the average amount of the code that is excessively complex at any level, and so a way to understand the relative complexity of different projects or parts of projects.