We present a translation from Fickle (a Java-like language allowing dynamic object re-classi.cation, that is, objects that can change their class at run-time) into plain Java. The translation is proved to preserve static and dynamic semantics; moreover, it is shown to be effective, in the sense that the translation of a Fickle class does not depend on the implementation of used classes, hence can be done in a separate way, that is, without having their sources, exactly as it happens for Java compilation. The aim is to demonstrate that an extension of Java supporting dynamic object re-classi.cation could be fully compatible with the existing Java environment.