Non final records

[Maurizio Cimadamore]

Hi Julian,
a record is just a wrapper around some data, which exposes nice 
semantics properties  - for instance, given a record Point(int x, int 
y), it is always the case that:

```
Point p = new Point(1, 2);
assertEquals(new Point(p.x(), p.y()), p);
```

(this is actually the basis of why derived creation can be expressed).

In other words, records are meant to be stateless beasts (and for a 
reason!). Of course you can still have array lists components in a 
record, which can be mutated (added to), but I'd say using records this 
way is non-idiomatic, can lead to suprising behavior (e.g. w.r.t. 
pattern matching) and is discouraged.

A great writeup on why records are the way they are can be found here:

https://nipafx.dev/java-record-semantics/

Cheers
Maurizio


On 25/01/2024 13:18, Julian Waters wrote:
> Hi all,
>
> Just a quick question:
>
> Why isn't modifying the contents of a record supported formally?
> (Without reflection and the like) Wouldn't it be helpful to be able to
> modify a record's fields? Is there any plan to allow doing so in the
> future?
>
> best regards,
> Julian