CleanJava: Language Design for the Simplification of Object- Based Reasoning

References are an integral part of popular object-oriented languages. They permit efficient data movement and parameter passing, and implement object identity. But their current use complicates reasoning by routinely introducing object aliasing. As a result, a significant body of research has focused on alias control techniques for object-oriented languages. This paper aims to simplify reasoning about objects by allowing programmers to ignore references in reasoning without losing the performance benefits they provide. It introduces a language design principle, cleanliness, that promotes the view of all variables as independent object values regardless of their implementations. To illustrate how this principle can be realized efficiently in practice, it describes the design of CleanJava. CleanJava is the result of re-engineering Java, focusing on four main areas of language design that involve references: object initialization, data movement, parameter passing, and the implementation of typically linked data structures.