Java Concurrency Tools View the Project on GitHub JCTools/JCTools Download ZIP File Download TAR Ball View On GitHub JCTools Java Concurrency Tools for the JVM. This project aims to offer some concurrent data structures currently missing from the JDK: SPSC/MPSC/SPMC/MPMC variations for concurrent queues: SPSC - Single Producer Single Consumer (Wait Free, bounded and unbounded) MPSC - Multi Produce