Add a unnamed interface to the current classdiagram by single-clicking on the interface icon in the tool bar and then clicking at the diagram pane (see Figure 6.1, “ Selecting the Interface tool ”).

Figure 6.1.  Selecting the Interface tool

Then double click on the interfaces name field to change it's name as shown in Figure 6.2, “ Interface model element on the Class Diagram ”

Figure 6.2.  Interface model element on the Class Diagram

and type a name for it (like TestInterface in this case). Press “Enter” when the name is complete. (You could also enter the name by going to the Properties Tab in the Details Pane after adding the interface.)

Add another interface with a different name by repeating the last 2 steps. Then single-click on the Generalization icon in the tool bar as shown in Figure 6.3, “ Generalization on the Class Diagram tool bar ”.

Figure 6.3.  Generalization on the Class Diagram tool bar

Move the mouse pointer to the subinterface, press the left mouse button and drag the generalization to the superinterface, where you release the mouse button. The screenshot of Figure 6.4, “ Generalization between two Interfaces. ” shows how your diagram should look now.

Figure 6.4.  Generalization between two Interfaces.

By clicking on the subinterface and the source tab properties pane, and then selecting Java Notation for the source tab, you can see that the interface actually extends it's superinterface.