Java Concurrency Tools for the JVM

 JCTools offers 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 Producer Single Consumer (Lock less, bounded and unbounded)
    * SPMC - Single Producer Multi Consumer (Lock less, bounded)
    * MPMC - Multi Producer Multi Consumer (Lock less, bounded)
  * An expanded queue interface (MessagePassingQueue):
    * relaxedOffer/Peek/Poll: trade off conflated guarantee on full/empty queue
      state with improved performance.
    * drain/fill: batch read and write methods for increased throughput
      and reduced contention