| Functor.java | Class | Implements function call-backs.
Functors may be defined for instance objects or classes.
The method is created on first use, which allows the invokee (class or instance)
to be omitted from the constructor.
The class name takes precedence over the instance.
If a functor is created with a particular instance, then that is used for all future calls;
if an object is provided, it is ignored. |