In Unified Modeling Language (UML) sequence diagrams, you can specify
class names and types for lifelines.
You must have a sequence diagram with lifelines open in the diagram
editor.
To specify the class name and type for a lifeline, in the Package
Explorer or Project Explorer view, click and
drag a Java™ class or interface onto a lifeline.
The lifeline head is updated with the Java class or interface name and type.