Computing Interfaces in Java

We investigate the separation between types and classes by putting to use a special feature of Java regarding classes, interfaces and inheritance. We propose an original method which, from a single inheritance class hierarchy, extracts a multiple inheritance interface hierarchy, which contains all the types of the original hierarchy, each class being linked to the interface representing its type. In the resulting structure, interfaces are well organized, and follow a natural multiple specialization, which would not have been possible using only the single inheritance which comes with Java. Our method is based on the use of a Galois lattice, which, as previous works have shown, is a reference for the elaboration of hierarchies. We introduce and justify the need for a new algorithm that efficiently builds an essential part of the Galois lattice.