Bug prediction has generated widespread interest for a long time. The general scenario have been many applications with different approaches. The raising of properties of programming languages made it necessary a study about the correlation between classes, packages and files. In order to improve the quality of code and the developers satisfaction. In the last 20 years there are studied many metrics to evaluate a coding and to limit bugs. In further detail for instance, the Chidamber and Kemerer (CK) object-oriented metrics suite based on coupling between objects, numbers of children or depth of an inheritance tree. We will focus on different levels of granularity (class, method or package), paying attention on a featuring selection like to reduce or to combine metrics.