An excellent presentation - http://www.javapolis.com/JP05Content/talks/day3/brian2/index.html and excellent site - http://www.cs.umd.edu/~pugh/java/memoryModel/index.html Locking optimization at Java 6 http://www-128.ibm.com/developerworks/java/library/j-jtp10185/index.html?ca=drs-tp4205