Suggestion regarding Null State Analysis in Project Valhalla

[Abdurasul Abduraimov]

Dear Team,

I am a big fan of Java and I’m eagerly awaiting the release of Project
Valhalla. I watched the Valhalla session from IntelliJ IDEA Conf 2025 (Day
1), where Rémi Forax discussed the "Null State Analysis" feature. As he
explained, the system defines three null states:

   1.

   *Null-restricted:* Integer! or String!
   2.

   *Nullable:* Integer? or String?
   3.

   *Unspecified:* Integer or String (with no warning)

I understand that due to Java’s large amount of legacy code, introducing
nullable and non-nullable types (as in Kotlin) is challenging, and the team
is prioritizing backward compatibility.

However, I’d like to propose an idea:
What if the *Unspecified* state also emitted a warning? This way, all types
would continue to be effectively nullable (as they are today), but
developers upgrading to future Java versions (where Valhalla is finalized)
would be encouraged to explicitly annotate their types. They could mark
types as *not-null* where appropriate, or accept the nullable default,
making their intentions clear.

This would parallel Kotlin’s philosophy, but in an inverse way:

   -

   In Kotlin: all types are *not-null* by default, nullable types must be
   explicitly declared.
   -

   In Java (with this proposal): all types would be *nullable* by default,
   but *not-null* types would be explicitly declared — with the added
   benefit of a warning to help modernize existing code.

I know it’s a bit unusual, but I believe this approach could strike a
balance between safety, clarity, and backward compatibility.

Thank you for your great work on Java!

Best regards,
Abdurasul Abduraimov
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