This class provides a thread safe map interface (by extending Hashtable) and adds a way to easily and synchronously
iterator over the list of values as an array.
A generic queue interface similar to the java.util.Queue interface in the JDK 1.5 API NOTE: the interface is not
complete with respect to the JDK version.
A class to model a flag that can be set once and only once If you have a boolean in class that should
really only be set once and only once (like a shutdown flag maybe), using this class might help your class stay
implemented correctly
NOTE: There is purposefully no way to reset the flag.