We define Junior as a Java framework kernel for reactive programming with broadcast events. We give Junior a formal semantics based on rewriting rule. We also describe three implementations of Junior. The first one, called REWRITE, is the direct implementation of the semantics rules. The second one is called REPLACE; it is more efficient than REWRITE as it reuses Java objects instead of always creating new ones. The third implementat- ion, called TURBO, optimises the number of syntax tree traversals and is adapted to situations where there are a large number of events. Finally, we discuss the extension of Junior to distributed contexts and compare it with the SugarCubes Reactive Java framework
