%T Communicating Java Threads Reference Manual %A Gerald H. Hilderink %E Andr\[`e] W. P. Bakkers %B Proceedings of WoTUG\-20: Parallel Programming and Java %X This document describes a csp package that contains the channel and composition classes in Java according to the CSP paradigm. The csp classes form a complete package that contains the necessary ingredients for concurrent programming with channels in Java. The channel and composition concepts are derived from CSp and are developed according to the object\-oriented paradigm. There is a clear pattern of concerns by means of object\-oriented techniques using inheritance, delegation, genericity , and polymorphism. This document is meant as a reference manual and gives background information about the realization of the csp classes. The use of the CSP channels in Java is illustrated by means of using building blocks.