[cs-szazz]

I'm not sure what it's taking about for the "with" feature: https://nipafx.dev/java-record-semantics/#with-blocks

In Kotlin data classes, it's already implemented (just called copy) https://kotlinlang.org/docs/data-classes.html#copying

[giaour]

"With" doesn't exist in Java, but it was introduced in C# 9.0 as part of the .NET implementation of records:

https://devblogs.microsoft.com/dotnet/c-9-0-on-the-record/#w...

I think the author is more saying that a "with" operator would fit into Java record semantics but might not be compatible with Lombok @Data classes or Kotlin data classes (though it looks from your link that Kotlin actually does have something very similar in the "copy" method).

[giaour]

Not sure why this is getting downvoted; if you look at the hypothetical “with” syntax in the original blog post, it is clearly borrowed from the C# implementation.

[kelnos]

The annoying thing about Java here is that it doesn't have default argument values, and doesn't allow you to name your arguments in function calls.

In Scala (I don't know Kotlin, but I assume it's similar) you could easily implement a copy() method yourself (and many people do if they need a case-class-like thing but can't use a case class) that behaves identically to the copy() method provided by a case class.

But the semantics of that copy() method require default argument values, and the ability to call functions using named arguments. Java doesn't have either of those, so instead of adding those features (I can understand the former being controversial), I guess the plan is to add entirely new syntax just for records, which IMO is a huge shame.

But it appears the "with" syntax is far from finalized, so it's possible they'll do something better.

[bcrosby95]

It was included because changing data using records (copying it except changing the fields you need to change) is a shitty experience, so rather than showing the code you have to write, they showed you code you may or may not in the future be able to write.

[dlbucci]

Seems like an odd thing to mention. They are arguing that records are better than data classes, but part of their argument is "maybe, in the future, at some point, I don't know, it will be as easy to do this thing with records as it already is with data classes, we'll only need to add new syntax and a new keyword to the language".

[krzyk]

Who is they?

You mean the article author? Yes, it was odd that he mentioned that, but besides that not a bad feature to have (but a bit wordy for my taste, I hope they'll change that).

[papercrane]

> I'm not sure what it's taking about for the "with" feature: ...

The author is referencing possible future work that can build on the current records implementation, and the work Brian Goetz is doing with pattern matching and record deconstruction. Goetz has put together a draft that shows how these could be combined.

https://github.com/openjdk/amber-docs/blob/master/eg-drafts/...

[stickfigure]

It's also implemented nicely, today, with Lombok:

    @Value @With
    public class Pair {
        int left;
        int right;
    }

    final Pair rightIs3 = somePair.withRight(3);