Java's implementation of checked exceptions has some issues, though.
* "Invisible control flow", where you can't tell from the call site whether or not a call might throw (you need to check the signature, which is off in some other file, or perhaps visible in an IDE if you hover).
* Java has both checked and unchecked exceptions, but they go through the same try-catch mechanism, failing to make a clean distinction between recoverable errors and unrecoverable bugs. (In e.g. Rust and Go, recoverable errors go through return values but unrecoverable errors go through panics.)
In the end, Java's exception design simultaneously requires a lot of effort to comply with, but makes it difficult to understand when you've successfully locked things down.
Never found this this to be a problem. It is really common to all implementations of exceptions, not just checked ones. And when you write code the compiler will yell at you. In monadic code,
People are used to that, and one common strategy is to not worry too much about exceptions and then wrap a big `try` block around everything near the outer boundary of your code. It’s good enough for many purposes and yields a high initial development velocity, but is comparatively fragile.
With Languages like Rust, Go, and Swift, only unrecoverable errors trigger the panic mechanism. Every call site where a recoverable error may occur is identifiable — in Rust via Result, `unwrap()`, the `?` operator, etc, in Go via returned Err (though unlike Rust you can discard them silently), and in Swift via the `try` operator.
You can still develop quickly by just unwrapping every Result, but unlike languages with invisible control flow, you can easily audit the codebase and go back to harden every site where a recoverable error may occur — yielding a level of robustness which is difficult to achieve in languages with unchecked exceptions.
> failing to make a clean distinction between recoverable errors and unrecoverable bugs
Recoverability is context specific. One persons panic may just be another error case for someone else. I think this is one thing that programmers miss when talking about this topic. It is really up to the caller of your function if something should panic. You can’t make that decision for them.
> One persons panic may just be another error case for someone else.
We can make a strong distinction between recoverable errors (e.g. this I/O operation may fail) versus unrecoverable errors that may leave the process in an unsound state, such as divide-by-zero or out-of-bounds array access[1].
There are some problem domains where even unrecoverable errors are not allowable, and programmers in those domains have to grapple with the panic mechanism.
But for the rest of us, it is useful to be able to distinguish between recoverable and unrecoverable errors — and to know how we have handled all possible sites which could result in recoverable errors.
[1] Joe Duffy explains it well: https://joeduffyblog.com/2016/02/07/the-error-model/#bugs-ar...
Checked exceptions are an awesome feature that more languages should have. Just like static typing is a good thing because it prevents errors, checked exceptions are a good thing because they prevent errors.