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Comment by BinaryIdiot | Hacker News Reader

My favorite part is the Java project that has an exception class called ThisShouldNeverHappenException [1]. Only in Java would someone create an exception class for a condition that should never happen :)

[1] https://github.com/TheProjecter/propidle/blob/f0d5320e2a3d46...

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Not just Java. I've seen similar classes in C++ and C# to indicate things which should never occur/are clearly bad programmer mistakes/... Think InternalErrorException/DevFailedError etc. Sometimes it's just a sane thing to do, and using such names means you don't need to write the dreaded 'should never happen' comment manually anymore.

To elaborate a bit, in C++ the relevant exception class is called `std::logic_error` (contrast with `std::runtime_error`). I like it. It is a bit more descriptive of the actual situation than "this should never happen".

In C#, I tend to use the built-in InvalidOperationException class -

https://msdn.microsoft.com/en-us/library/system.invalidopera...

Isn't that what assertions are for?

Assertions can be disabled at runtime. If your goal is to call out the fact that something has gone fundamentally wrong with your program's state, an exception is the way to go.

in Python, running with `-O`, from .pyo files, or equivalent settings in your webserver will all disable assertions. surprise!

I don't think it is a programmer error. Many times when you program against some less reliable API or doing some network stuff the variety of exceptional situations can be really overwhelming. Such exceptions can be some sort of sink to evaluate later whether you still need to improve the code to handle some very specific corner cases.

Right. The best ones are the ones that tell not only that something is wrong, but explicitly says what should be fixed.

Yep. There's What A Terrible Failure exception in the Android codebase (i.e. "throw wtf"). http://developer.android.com/reference/android/util/Log.html...

My code made the Android OS throw this once. Not a terribly useful error to resolve.

Edit: My mistake. I misremembered. It's a logging function. I should have actually read the link I provided.

There's http://docs.oracle.com/javase/6/docs/api/java/lang/IllegalSt... that could be used in this case.

Exceptions in Java are to raise them. In Go there is a panic() call, which semantically sounds to me very much like ThisShouldNeverHappenException. It doesn't make Go worse and Java better though.

I would use AssertionError exception for that.

Why man has nipples if he does not breast feed?

I could ask you the very same question.

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