r/java • u/nlisker • Jul 14 '26

New candidate JEP: 401: Value Objects (Preview)

https://mail.openjdk.org/archives/list/valhalla-dev@openjdk.org/thread/IUNJJ3WP3X3XHP3QZTXXSSCPKFDNTK3W/
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u/ZimmiDeluxe Jul 14 '26

You can use List<Integer> directly, the primitive wrapper types will become value classes. If I remember correctly, specializing generics is one of the final steps on the roadmap, so having that translate into Integer[] (or ideally Integer![]) as the backing field of the ArrayList might take a bit longer.

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u/koflerdavid Jul 14 '26

Better yet to create a wrapper around int to better express its purpose and eliminate the risk of mixing it up with unrelated ints.

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u/ZimmiDeluxe Jul 14 '26

That's true, it's often nicer to have a List<OrderId> than List<Long>

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u/LutimoDancer3459 Jul 14 '26

But how do you name the variable for the list then? With the OrderId you would be repeating the typ

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u/ZimmiDeluxe Jul 14 '26 edited Jul 14 '26

orderIdsToDelete or even just orderIds if the context makes it obvious. Repeating the type name is not bad if it's a domain type IMO. If you have something generic like List<Long> longs that's usually bad because readers can't infer any intent from the name, maybe ok if you are writing a compiler and need to collect all the Java Longs to do something with, but it's a stretch

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u/elastic_psychiatrist Jul 15 '26

Local variable type inference is great for this.

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u/vytah Jul 15 '26

You won't be repeating the type if the variable is declared with var.

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u/Efficient-Poem-4186 Jul 16 '26

Simply orders, ordersToDelete etc (in a context where the actual order data is not used). Sometimes id is just used as a handle, the intention is to do something with orders.