Reports double-checked locking. For a discussion of double-checked locking and why it is unsafe, see http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

Use the checkbox below to ignore double-checked locking on volatile fields. Using a volatile field for double-checked locking works correctly on Java 5 virtual machines, but probably does not have any performance advantages over plain full synchronization of the accessor method.