Lightweight confinement for featherweight Java

Abstract

Confinement properties impose a structure on object graphs which can be used to enforce encapsulation properties essential to certain program optimizations, modular reasoning, and software assurance. This paper formalizes the notion of confined type in the context of Featherweight Java. A static type system that mirrors the informal rules of Grothoff et al [17] is proven sound. The definition of confined types is extended to confined instantiation of generic classes. This allows for confined collection types in Java and for classes that can be confined post hoc. Confinement type rules are given for Generic Featherweight Java, and proven sound.