Open Access Te Herenga Waka-Victoria University of Wellington
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Generic Ownership Types for Java and the Collections Framework

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posted on 2021-11-14, 03:43 authored by Khalifa, Ahmed Aziz

Generic programming has turned out very useful in the development of reusable software. With the Java programming language, genericity is not only meant for reusability, but also for type-safety. Java generics constrain a container object (e.g., list, hash table) to store objects of a pre-specified data type. Nevertheless, safe programming with aliasing (multiple pointers in a program may point to the same object) is still a concern in object-oriented programming language research. A pointing object can mutate the state of the aliased object, reflecting the changes to all of the other pointers (aka aliases) thus affecting their behaviour. As programs grow larger and more complex, such changes in behaviour can be undesirable and difficult to detect and reason about. With respect to container objects, the iterator pattern critically violates encapsulation, allowing aliases to the state (and thereof the components) of its container.  Object ownership is one of the well-researched paradigms in the area of alias management. Ownership types support hierarchical object encapsulation rather than the traditional class-level encapsulation. This thesis introduces an extension of Java 6 with support for ownership types as supplementary generic types. That is, Java generics are extended with the ability of carrying ownership information. This extension provides generic ownership support for all of Java; that is, all major language features are addressed so that programs can safely manage and express their aliasing properties. The resulting language is expressive enough to support common programming idioms, with little programming and runtime overhead. We evaluated the programmability of the language by refactoring a major (the most essential) portion of the Java Collections Framework. We also evaluated the performance impact of our refactoring by conducting a small micro-benchmark study to measure the performance time overhead the refactored collections may impose.


Copyright Date


Date of Award



Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Computer Science

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level


Degree Name

Doctor of Philosophy

ANZSRC Type Of Activity code

970108 Expanding Knowledhe in the Information and Computing Sciences

Victoria University of Wellington Item Type

Awarded Doctoral Thesis



Victoria University of Wellington School

School of Engineering and Computer Science


Potanin, Alex; Noble, James