Experienced Java developers are expected to have a collection of design patterns in their toolbox. Sun's certification exam for Java architects already explicitly tests for knowledge of the Gang of Four's patterns. When the exam is rewritten for release next year, other enterprise patterns will be added. Mark Johnson and Inderjeet Singh copresented a session on J2EE design patterns for enterprise applications. Their presentation concentrated on the patterns used to construct the Java Pet Store application available on Sun Microsystems Inc.'s site.