JPred resolves several limitations in prior approaches to predicate dispatch. First, JPred retains Java's modular typechecking and compilation strategies; prior languages with predicate dispatch have required the whole program to be available for typechecking and compilation. Second, JPred employs general-purpose, off-the-shelf decision procedures to perform precise reasoning about predicates at compile time. As a result, JPred's type system allows several useful programming idioms that are spuriously rejected by prior languages.
Modularly Typesafe Interface Dispatch in
JPred (FOOL/WOOD 2006)
Christopher Frost and Todd Millstein
Dispatch (OOPSLA 2004)
An Eclipse plugin for the JPred compiler is available here.
The JPred compiler is implemented as an extension in the Polyglot extensible compiler framework. It extends the Polyglot for Java 1.5 extension, which allows Polyglot to support the Java 1.5 language features.
The TOPLAS 2009 paper above is currently the best documentation for the language.