Joda-Beans VS Checker Framework

That means I don't forget about fields (as can happen if you're just doing `person.setX()` all the time). It's easy to see what is what when reading it. I can delete fields I don't want to initialize at the time. Yes, maybe immutable objects are the One True Way, but C# lets me choose (I can label properties with an initializer `init` rather than a setter `set` and then they're immutable).

Kotlin offers stuff like this too because it's really useful toward creating code that's easy to create and maintain. Go also lets you initialize structs in a similar fashion.

Java has come back to us a decade or more late with records. They're not bad, but they're only offering one thing. They don't cover what C#, Kotlin, Go, and other languages have offered for so long.

The annoying thing about Java is that it doesn't feel pragmatic a lot of the time. It feels like the language hates stealing ideas from others. It's Java: people steal ideas from Java, not the other way around. People do crazy things just to get POJOs including Immutables (http://immutables.github.io), AutoValue (https://github.com/google/auto/), Lombok (https://projectlombok.org), Joda Beans (https://www.joda.org/joda-beans/), and maybe more. They generate lots of code at compile time or do funky runtime stuff.

It just feels like Java misses the pragmatic stuff and still kinda doesn't want to handle that. I feel a bit silly harping on things like POJOs and setting data on a new object, but that's a big part of day-to-day stuff and it definitely pushes users away from Java towards languages that seem "better" simply because they don't have Java's oddly strong attachment to not offering simple value objects. Yes, again, records do something - but it feels like Java ignored how people are using Kotlin, Go, C#, and more and didn't go for something that would have been as widely applicable and pragmatic as it could have been.

Java has a lot of great stuff like great GCs (yes), lots of cool research, great performance, and Project Loom is really exciting. I just wish the language would lean a little more practical.

I know I've been talking about properties a bunch, but let's look at Java. Java Beans are terrible - so terrible that the community has a number of workarounds. Immutables (https://immutables.github.io) lets you generate builders, Lombok (https://projectlombok.org) has their annotations that do runtime and IDE magic, there's Joda-Beans (https://www.joda.org/joda-beans/), there's the new Java Records if you want immutable-only and non-compatibility with lots of libraries, there are people using Kotlin for their data classes and Java for other things... Properties are this simple thing that lets C# work with the whole getter/setter pattern without being horribly annoying - there's just this weird { get; set; } thing that I can ignore because I don't care.

I’m not familiar enough with kotlin to comment fully but from your description the checker framework [0] appears to do the same thing in Java.

I confess I’m not fond of checker framework. I find the error messages can be obtuse but it is very effective.

0 - https://checkerframework.org/

It is interesting! I experimented with creating a bad borrow checker for Java using annotations from

https://checkerframework.org/

It supports some level of substructural types using must-call annotations,

https://checkerframework.org/manual/#resource-leak-checker

Lombok is not a compiler extension. Compiler extensions, aka annotation processors, are offered only specific capabilities that ensure that they preserve the Java language specification. Particularly, code that compiles successfully with an extension also compiles without it (perhaps requiring other classes to be available) and it compiles down to the same bytecode. Annotation processors are used to implement pluggable type systems (e.g. https://checkerframework.org) or to generate other classes (e.g. https://immutables.github.io/).

Unlike compiler extensions, Lombok compiles source files that do not conform to the Java language specification. Lombok is an alternative Java Platform language, like Clojure or Kotlin or Scala, except that it's a superset of the Java language. However, rather than forking `javac` source code and modifying it to compile Lombok source files, the Lombok compiler modifies `javac`'s operation by hacking into its internals and modifying them as it runs to compile Lombok sources rather than Java sources.

Having alternative Java Platform languages is perfectly fine. The problem with Lombok is that it doesn't present itself as such but as a library or a compiler extension even though it violates the Java language specification in ways that compiler extensions are forbidden from doing.

And then I found (thanks Oracle), https://checkerframework.org/ zomg, this thing is awesome. Pluggable Type Systems!

Java should adopt something like the Checker Framework Nullness Checker in its first-party tooling.

https://github.com/typetools/checker-framework

And modern (real, non-android) Java via project amber and so on has gone more and more quasi functional with its immutability and sealed and record types for effective sum types, as well as its pretty cool type-use annotation extensible static type checks.

Checkerframework - a really academic take, and as one might expect from such a thing, backed by tons of papers and analysed to perfection. Specifically, this is the only framework I'm aware of that realizes nullity is a little more complicated than just a boolean yes-or-no; just like generics actually have 4 flavours for any given type: List, List, List, and List are all 4 important and unique, and nullity is no different. Specifically, it can occur that you want to write a method that ought to accept both lists of nullable strings as well as list of nonnull strings, and needs to 'convey' this nullity again on its output. You can either attempt to lift along the existing generics system in java which I think is your intent, but it's not actually all that easy to do this. After all, T extends @Nullable Number super @NonNull Number, or whatnot, isn't legal java. So you.. really just can't do that. Checker Framework solves this problem by introducing the @PolyNull annotation, which still isn't perfect but covers almost all real world use cases you can think of. I'm missing any acknowledgement in your documentation. An oversight, or, something you hadn't thought of yet? You're in good company: Both eclipse and intellij's engineers, when I asked them about it, just hadn't realized it was a thing. Point is: If you think the primary problem with e.g. eclipse's and intellij's take is that they lack academic rigour - checkerframework has you beat.

NullAway or the Checker Framework should greatly help eliminate the issue. Also, when Java gets value types you should be able to define your own non nullable value types and use them safely.