Add nullability annotations

[matthewadams]

Proposed change

Please annotate the API, including return types and parameters, with @javax.annotations.NonNull or @javax.annotations.Nullable as appropriate so that users of the API know what can and can't be null.

Use case

My use case is when using jnats from kotlin, but it applies to any user of jnats. For example, I discovered that io.nats.client.api.KeyValueEntry has a method

public byte[] getValue() {
  return value;
}

that allows for the returned byte[] to be null. Kotlin builds nullability into the type system for compile-time checking, and if Java APIs include these annotations, the kotlin compiler can inform the developer better about nullability.

Contribution

No response

[scottf]

@matthewadams We are currently looking at how we can improve integration with Kotlin, and this will make the list.

[MauriceVanVeen]

Have an example of using JetBrains' annotations here: 869012b

Tried out javax and jakarta annotations for @NotNull as well, but those didn't seem to be recognized.

Without the @NotNull annotation you need to technically handle the case where entry.operation == null, even if it's not possible to be

Adding JetBrains' @NotNull solves that.

Could be an option to use those.

[MauriceVanVeen]

An alternative that works as well: org.checkerframework:checker-qual using @NonNull.

[cbasener]

Maybe this is also an option?
https://jspecify.dev/