jclouds/jclouds — comment on commit ff9849ec1aa57f784d6965f4550d1d88ece37012
File: core/src/main/java/org/jclouds/JcloudsVersion.java line 45
By jclouds:

my favorite singleton pattern is enum :)
http://stackoverflow.com/questions/70689/efficient-way-to-implement-singleton-pattern-in-java