Active Class

An active class has instances, each of which executes and controls its own thread of control. Method invocations may execute in a client's thread or in the active object's thread. A good example of this is a command processor that accepts command objects from the outside and then executes the commands within its own thread of control.

The notation for active classes has changed from UML 1 to UML 2, as shown in Figure 5.21. In UML 2, an active class has extra vertical lines on the side; in UML 1, it had a thick border and was called an active object.