This paper describes a run-time specialization system for the Java
language.  One of the main difficulties of supporting the full Java
language resides in a sound yet effective management of references to
objects.  This is because the specialization process may share
references with the running application that executes the residual
code, and because side-effects through those references by the
specialization process could easily break the semantics of the running
application.  To cope with these difficulties, we single out a set of
requirements that ensures correct run-time specialization.  Based on
them, we design and implement a run-time specialization system for the
Java language.  Our preliminary experiments reveal, for instance,
approximately 20-25% speed-up factor for a ray-tracing application.