1 <p> This method may contain an instance of double-checked locking.
2 This idiom is not correct according to the semantics of the Java memory
3 model. For more information, see the web page
4 <a href="http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html"
5 >http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html</a>.</p>