Chaplin ACT is a Java class transformer which brings several modern language concepts into Java: contexts, composites, roles, traits (mixins), runtime type conversion, dynamic method signatures, method and field aggregators, etc. Using these concepts makes designing loosely-coupled applications and writing cohesive code easier. Chaplin can work either as a JVM agent or as a post-compilation class transformer. It does not introduce any new syntax. All functionality is implemented by means of the standard Java language elements.