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Performance Considerations
A significant amount of system resources and execution time are used when you throw or handle an exception. Throw exceptions only to handle truly extraordinary conditions, not to handle predictable events or flow control. For example, your application can reasonably throw an exception if a method argument is invalid because you expect to call your method with valid parameters. An invalid method argument means something extraordinary has occurred. Conversely, do not throw an exception if user input is invalid because you can expect users to occasionally enter invalid data. In such a case, provide a retry mechanism so users can enter valid input.
Throw exceptions only for extraordinary conditions, then catch exceptions in a general purpose exception handler that applies to the majority of your application, not a handler that applies to a specific exception. The rationale for this approach is that most errors can be handled by validation and error handling code in proximity to the error; no exception needs to be thrown or caught. The general purpose exception handler catches truly unexpected exceptions thrown anywhere in the application.
In addition, do not throw an exception when a return code is sufficient; do not convert a return code to an exception; and do not routinely catch an exception, ignore it, then continue processing.
