You can specify a Java class in the PDM, and then link it to a Java class in an OOM. The OOM must be open in the current Workspace to be available for linking.
When you link an abstract data type to a Java class, a shortcut is created which allows you to access the properties of the Java class from within the PDM.
The abstract data type is now linked to the Java class, and the class name is displayed in the Class box.