26 July 2021

Why you should care

You should not ignore exceptions. It can be tempting to be lazy when catching exceptions and do something like this: (see example below).

Developers should avoid this. In almost all cases, it’s inappropriate to catch generic Exception or Throwable (preferably not Throwable because it includes Error exceptions). It’s dangerous because it means that exceptions you never expected (including runtime exceptions like ClassCastException) get caught in app-level error handling. It obscures the failure- handling properties of your code, meaning if someone adds a new type of exception in the code you’re calling, the compiler won’t point out that you need to handle the error differently. In most cases you shouldn’t be handling different types of exceptions in the same way.

The rare exception to this code insight is test code and top-level code where you want to catch all kinds of errors (to prevent them from showing up in a UI, or to keep a batch job running). In these cases, you may catch generic Exception (or Throwable) and handle the error appropriately. Think carefully before doing this, though, and put in comments explaining why it’s safe in this context.

How we detect

CAST Highlight counts one occurrence each time a catch instruction is dealing with generic exception type : Throwable and Exception.

 try {
someComplicatedIOFunction(); // may throw IOException
someComplicatedParsingFunction(); // may throw ParsingException
someComplicatedSecurityFunction(); // may throw SecurityException
// phew, made it all the way
} catch (Exception e) { // I'll just catch all exceptions
handleError(); // with one generic handler!
}

References

https://source.android.com/setup/contribute/code-style#dont-catch-generic-exception

About CAST and Highlight’s Code Insights

Over the last 25 years, CAST has leveraged unique knowledge on software quality measurement by analyzing thousands of applications and billions of lines of code. Based on this experience and community standards on programming best practices, Highlight implements hundreds of code insights across 15+ technologies to calculate health factors of a software.

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