BatakJava']Java: An Object-Oriented Programming Language with Versions

Programming with versions is a recent proposal that supports multiple versions of software components in a program. Though it would provide greater freedom for the programmer, the concept is only realized as a simple core calculus, called..VL, where a value consists of lambda-terms with multiple versions. We explore a design space of programming with versions in the presence of data structures and module systems, and propose BatakJava, an object-oriented programming language in which multiple versions of a class can be used in a program. This paper presents BatakJava's language design, its core semantics with subject reduction, an implementation as a source-to-Java translator, and a case study to understand how we can exploit multiple versions in BatakJava for developing an application program with an evolving library.