Multiverse is a Software Transactional Memory implementation that can be used in Java but also in other languages running on the JVM like Scala or Groovy. Essentially it is a framework that allows different STM implementation (with different featuresets or performance characteristics) to be used under the hood. The main STM implementation is multiverse-alpha..
POM file JAR file Javadoc'org.multiverse:multiverse-performance-tool:0.6'