Can I use any data type in a `when` statement?

# getting-started

[Florian]

Can I use any data type in a when statement?

[Marko Mitic]

any that has proper .equals function

[karelpeeters]

And if it doesn't you can still use in.

[Florian]

I can create types without .equals, right?

[Alowaniak]

It'll always have an .equals; it's just that it will use object identity by default or however it's called

[Alowaniak]

also if you create a data class (since you're talking about "any data type") it will have a "proper" equals

[Florian]

OK right, but the when will compile?

[Florian]

In the first case

[Marko Mitic]

yeah

[Florian]

OK, thank you

[Florian]

But why is it that when is so much more flexible than switch? Surely the designers must have had a reason why they made switch so limited.

[Florian]

And now `when`can do pretty much anything

[Marko Mitic]

java just copied C's switch, which was a standard at that time

[Marko Mitic]

it's hard to change it without breaking compatibility but they could have added their own when

[Marko Mitic]

they are just kinda slow and bureaucratic with changing the language

[Florian]

OK, I see

[karelpeeters]

To be fair the Kotlin when is not that powerful either, other languages like Scala, C#, Rust and others have actual pattern matching.

[Florian]

What does pattern matching mean here?

[Marko Mitic]

https://docs.scala-lang.org/tour/pattern-matching.html

[Mike]

And in JDK12, they are beginning the process of improving switch. Much closer to Groovy switch/Kotlin when.

Details: https://www.oracle.com/technetwork/java/javase/12-relnote-issues-5211422.html#JDK-8192963

And in future versions, they intend to introduce forms of pattern matching.

[Mike]

https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8192963