K.U.Leuven JCHR is an embedding of Constraint Handling Rules (CHR) in Java. The multi-paradigmatic integration of declarative, forward chaining CHR rules and constraint (logic) programming within the imperative, OO host language Java offers clear synergetic advantages to the software developer. High performance is achieved through an optimized compilation to Java code. The rule engine is suited for the high-level development of expert systems, constraint solvers, constraint-based algorithms, etc