Designing robust java programs with exceptions

Exception handling mechanisms are intended to help developers build robust systems. Although an exception handling mechanism provides a basis for structuring source code dealing with unusual situations, little information is available to help guide a developer in the appropriate application of the mechanism. In our experience, this lack of guidance leads to complex exception structures. In this paper, we reflect upon our experiences using the Java exception handling mechanism. Based on these experiences, we discuss two issues we believe underlie the difficulties encountered: exceptions are a global design problem, and exception sources are often dif-ficult to predict in advance. We then describe a design approach, based on work by Litke for Ada programs, which we have used to simplify exception structure in existing Java programs