Exceptions: When Things Go Wrong

10.5 Error Handling and Robust Program Design

An important element of program design is to develop appropriate ways of handling erroneous and exceptional conditions. As we have seen, the JVM will catch any unchecked exceptions that are not caught by the program itself. For your own (practice) programs, the best design may simply be to use Java’s default exception handling. The program will terminate when an exception is thrown, and then you can debug the error and recompile the program.

On the other hand, this strategy would be inappropriate for commercial software, which cannot be fixed by its users. A well-designed commercial program should contain exception handlers for those truly exceptional conditions that may arise.

In general there are three ways to handle an exceptional condition that isn’t already handled by Java (Table 10.3). If the exceptional condition cannot be fixed, the program should be terminated, with an appropriate error message. Second, if the exceptional condition can be fixed without invalidating the program, then it should be remedied and the program’s normal execution should be resumed. Third, if the exception cannot be fixed, but the program cannot be terminated, the exceptional condition should be reported or logged in some way, and the program should be resumed.