Define Exception Classes in Terms of a Caller’s Needs

There are many ways to classify errors. We can classify them by their source: Did they come from one component or another? Or their type: Are they device failures, network failures, or programming errors? However, when we define exception classes in an application, our most important concern should be how they are caught.

Let’s look at an example of poor exception classification. Here is a try-catch-finally statement for a third-party library call. It covers all of the exceptions that the calls can throw: