Critical path analysis cannot be performed if cyclical dependencies exist between the activities and constraints in your Gantt data model. The IlvCriticalPathCalculator.computeSchedule() method will throw an IlvConstraintCycleException if such a cyclical dependency is detected. By contrast, the IlvGanttModelScheduler class does not directly throw exceptions when a cyclical dependency is found. Instead, it notifies its currently registered error handler of the problem. This allows you to easily implement a custom error handler that can inform the user in a manner that is appropriate to your application's user interface. The default error handler simply logs the exception. The following code shows a custom error handler that displays detected cycles in a Swing JLabel object: