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M.D.: Object and reference immutability using Java generics

By Yoav Zibin, Alex Potanin, Mahmood Ali, Shay Artzi and Michael D. Ernst

Abstract

A compiler-checked immutability guarantee provides useful documentation, facilitates reasoning, and enables optimizations. This paper presents Immutability Generic Java (IGJ), a novel language extension that expresses immutability without changing Java’s syntax by building upon Java’s generics and annotation mechanisms. In IGJ, each class has one additional type parameter that is Mutable, Immutable, or ReadOnly. IGJ guarantees both reference immutability (only mutable references can mutate an object) and object immutability (an immutable reference points to an immutable object). IGJ is the first proposal for enforcing object immutability within Java’s syntax and type system, and its reference immutability is more expressive than previous work. IGJ also permits covariant changes of type parameters in a type-safe manner, e.g., a readonly list of integers is a subtype of a readonly list of numbers. IGJ extends Java’s type system with a few simple rules. We formalize this type system and prove it sound. Our IGJ compiler works by typeerasure and generates byte-code that can be executed on any JVM without runtime penalty

Topics: Categories and Subject Descriptors, D.1.5 [Programming Techniques, Object-oriented Programming, D.2.1 [Software Engineering, Requirements / Specifications[Languages, D.3.3 [Programming Languages]Language Constructs and Features General Terms, Design, Languages, Theory Keywords, const, Generic, IGJ, Immutability, Java, Readonly
Year: 2007
OAI identifier: oai:CiteSeerX.psu:10.1.1.353.4193
Provided by: CiteSeerX
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