Ensuring Correctness of Java Frameworks A Formal Look at JCF

In this paper we propose a novel approach to speci cation development and veri cation of object oriented frameworks employing separate interface inheritance and implementation inheritance hierarchies In particular we il lustrate how our method of framework speci cation and veri cation can be used to specify Java Collections Framework which is a part of the standard Java Development Kit and ensure its correctness We propose to as sociate with Java interfaces formal descriptions of the behavior that classes implementing these interfaces and their subinterfaces must deliver Verify ing behavioral conformance of classes implementing given interfaces to the speci cations integrated with these interfaces allows us to ensure correctness of the system The characteristic feature of our speci cation methodology is that the speci cation language used combines standard executable statements of the Java language with possibly nondeterministic speci cation statements A speci cation of the intended behavior of a particular interface given in this language can serve as a precise documentation guiding implementation de velopment Since subtyping polymorphism in Java is based on interface in heritance behavioral conformance of subinterfaces to their superinterfaces is essential for correctness of object substitutability in clients As we view interfaces augmented with formal speci cations as abstract classes verifying behavioral conformance amounts to proving class re nement between spec i cations of superinterfaces and subinterfaces Moreover the logic frame work that we use also allows veri cation of behavioral conformance between speci cations of interfaces and classes implementing these interfaces The uniform treatment of speci cations and implementations and the relation ships between them permits verifying correctness of the whole framework and its extensions