On Access Restriction with Java Wildcards
Mirko Viroli, DEIS, Alma Mater Studiorum
- Università di Bologna, Italy
Giovanni Rimassa, Whitestein Technologies AG, Zurich, Switzerland
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REFEREED
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Abstract
Java wildcards is a new programming mechanism shipped with the Java
5.0 release,
introduced to provide a flexible subtyping mechanism for generic types.
Safety is retained
by providing rather peculiar and non-trivial mechanisms to restrict
access to a
class functionalities (methods and fields), which are currently not
deeply described in
the Java Language Specification. In this paper we develop on the theory
of variant
parametric types from which wildcards originated, and study a framework
to describe
these access restriction issues in detail, promoting the understanding
and fruitful exploitation
of this new programming concept.
Our work is both technical and conceptual. On the one hand, we provide
an abstract
characterisation of formal rules to access restriction, then instantiated
to the particular
implementation of wildcards in current Java. On the other hand, we
show that such a
characterisation induces a natural description and understanding
of access restriction
in terms of the ability of (instances of) a generic class to produce/consume
elements
of the abstracted type.
Note: Due to the typographical sophistication of this article, no HTML version is available. Please use the PDF version.
About the authors
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Mirko Viroli is a researcher associated
with DEIS department,
Alma Mater Studiorum - Università di Bologna, Italy. His interests
cover advanced features of object-oriented programming
languages, and engineering of concurrent and agent-based systems.
He can be reached at mirko.viroli@unibo.it.
See also
http://www.ingce.unibo.it/˜mviroli. |
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Giovanni Rimassa is employed
by Whitestein Technologies AG,
Switzerland, in a senior researcher position. He leads the development
of infrastructures and APIs for agent-based systems. He can
be reached at gri@whitestein.com.
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Cite this article as follows: Mirko Viroli and Giovanni Rimassa: “On
Access Restriction with Java Wildcards”, in
Journal of Object Technology, vol. 4, no. 10, Special Issue: OOPS Track
at SAC 2005, Santa Fe USA, December 2005, pp. 117-139 http://www.jot.fm/issues/issue_2005_12/article6
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