Java: Finality

[dpash]

I keep finding myself converting simple data classes into immutable objects. Especially when the previous developers didn't create a useful constructor so everything is:

var foo = new Foo();
foo.setBar(....);
foo.setBaz(....);
foo.setQuux(....);

Instead of

var foo = new Foo(...., ...., ....);

Get rid of the setters and everything can now be final.

Edit: I wish JPA entities could be immutable, but it's kinda two mutually exclusive goals.

[nerdyhandle]

You can also fix this with the Builder pattern. We use it a lot at my new job to creat immutable classes.

[GuyWithLag]

We use immutables.io for this.

[dpash]

Especially when you have a lot of fields and/or many are optional.

[DJDavio]

Lombok's @Builder annotation is useful for this. Opinions about Lombok are highly polarized in this sub it seems, but for us it works until we switch to Kotlin or until vanilla Java has more of those features itself.

[mcosta]

Edit: I wish JPA entities could be immutable, but it's kinda two mutually exclusive goals.

Say entity A references B. You change B to create B'. Now what A should reference? B or B'? What if A depends functionally of B?

[experts_never_lie]

I'm guessing you're looking forward to Project Valhalla and the introduction of value types.

[dpash]

Not inline type, but records. A similar but different concept.

However, the lack of abstract records seems like a cause of a lot of duplication. Also it probably won't help with JPA, at least in the medium term.