Class diagrams
Unified Modeling Language (UML) has become the developer's choice of tools for object-oriented design. Many types of diagrams are defined by UML, but here we'll only cover class diagrams and associations between classes. This tutorial will use IBM Rational XDE to display the different diagrams.

In class diagrams, classes are represented as boxes with three compartments:

The top section in a Class object contains the class name; if the class is abstract, then the name is italicized. The middle section contains the class attributes. The bottom section contains the class methods or operations. Like the class name, if a method is abstract, its name is italicized.

Associations between classes
Any interaction between classes is shown by a line drawn between the classes. A simple line indicates an association. The relationship between the classes can be modified to provide information about the association. The following diagram show the different types of associations that you will need to understand: