Suppose you have a method with some pre and post-conditions. Is it ok to create an exception class for each pre-condition that is not accomplished? For example: Not accomplishing pre1 means throwing a notPre1Exception instance.
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Suppose you have a method with some pre and post-conditions. Is it ok to create an exception class for each pre-condition that is not accomplished? For example: Not accomplishing pre1 means throwing a notPre1Exception instance.
Yes and no.
Yes – Violating a precondition is certainly an appropriate time to throw an exception. Throwing a more specific exception will make catching that specific exception simpler.
No – Declaring a new exception class for every precondition in your program/api seems way overkill. This could result in hundreds or thousands of exceptions eventually. This seems a waste both mentally and computationally.
I would recommend throwing exceptions for precondition violations. I would not, however, recommend defining a new exception for each precondition. Instead, I would recommend creating broader classes of exceptions that cover a specific type of precondition violation, rather than a specific precondition violation. (I would also recommend using existing exceptions where they fit well.)