is there a better way of declaring that my function will thr

Question

is there a better way of declaring that my function will throw an exception without using a annotation Example I use the`Throw` annotation ``` Throws NoSuchAlgorithmException class private fun generateKeyPair KeyPair ```

diesieben07 · Answer

No there is not Since this feature only exists for Java interoperability there is no direct language feature for it

Hexa · Answer

okay so there is no Kotlin way of doing this at all

diesieben07 · Answer

No Since Kotlin does not have checked exceptions there is no need for it What are you trying to achieve

Hexa · Answer

just trying to convert java code to kotlin

Hexa · Answer

so I can just get a way with using this ``` private fun generateKeyPair KeyPair ```

diesieben07 · Answer

Yes

diesieben07 · Answer

Unless you want to call the function from Java in which case you should keep the `Throws` annotation

Hexa · Answer

what happens when I call `generateKeyPair` function and it throws an exception does Kotlin just ignore it

diesieben07 · Answer

Exceptions in Kotlin behave like RuntimeExceptions in java

diesieben07 · Answer

If nobody catches them they will end up in the thread s UncaughtExceptionHandler

ursus · Answer

this always bothered me since it hides for example io exceptions when working with files etc

diesieben07 · Answer

It solves more problems than it creates imho

Sam · Answer

< ursus> I had the same question a while back check this response from Roman

Sam · Answer

Sam · Answer

In my case i opted to have a Type convey the result or error Result lt T gt or something like that

Sam · Answer

Callers of my API understand the error possibility while trying to handle the success case

ursus · Answer

< diesieben07> < elizarov> while I do agree with you modeling the error into return type is best even kotlin std functions for Files do throw

diesieben07 · Answer

Yes they do throw But checked exceptions bring all kinds of problems Kotlin uses lambdas and higher order functions heavily If you have checked exceptions you cannot call any functions that throw inside those lambdas because the lambda itself does not throw unless you catch the exception right there in the lambda

diesieben07 · Answer

That is one reason for unchecked exceptions

ursus · Answer

right but then the std api is wrong i e it appears File readBytes wont crash I need atleast a lint or something

diesieben07 · Answer

Define won t crash

diesieben07 · Answer

It won t crash unless there is an IOException which is an exceptional state

ursus · Answer

yes but expected exeptional state

ursus · Answer

only unexpected things should crash imo

diesieben07 · Answer

What classifies expected Is we ran out of memory unexpected

ursus · Answer

Depends on the domain Would you crash the app if your network request failed

diesieben07 · Answer

No so I add `catch` blocks

ursus · Answer

yes but you dont know to do that unless you look at source

diesieben07 · Answer

If I am reading a file I know that that can fail

diesieben07 · Answer

Example I am reading from an `InputStream` can that fail or not The answer depends on where the data comes from Is it a `ByteArrayInputStream` Then it can t fail

diesieben07 · Answer

Stuff like this cannot be reasonably exposed in the language this needs to be handled through documentation Look at any decently sized Java application and you will see stuff like this ``` try stuff catch IOException e throw AssertionError impossible ```

ursus · Answer

thats just a coincidence for Files pick any other custom api

ursus · Answer

Im not arguing for check exceptions Im arguing for tooling to not forget handling expected errors to which you have no knowledge of unless you look at source doc since the world is not ready yet to abandon them

diesieben07 · Answer

Okay but then you have the same problem How is the IDE supposed to know that this error will be handled further up the call stack

ursus · Answer

I see your point that Throws and doc is the same thing which can be out of date or forgot

ursus · Answer

maybe some static analysis for throw keyword

diesieben07 · Answer

I am not a tooling expert not sure how feasible that is

ursus · Answer

me neither but Ive forgot to add try catch in kotlin few times already