With JDK 26 / JEP 500 starting to prevent final field mutation through reflection, it is important that Java projects stop employing that practice. Whether it is for dependency injection, serialization, cloning, or general hackery, alternatives need to be explored.

JEP 500: https://openjdk.org/jeps/500
Inside Java Newscast #101: https://www.youtube.com/watch?v=bdHkbEIdBAs

~~~ Chapters ~~~~~

0:00 Intro
1:00 Final Field Mutation
1:57 Platform Serialization
3:08 Serialization
6:39 Dependency Injection
7:14 Cloning
8:26 Embracing Constructors

Tags: #Java #OpenJDK #Reflection #Integrity

Java (Official Oracle)

JDK 26 is restricting final field mutation via reflection, and developers need to adapt. The video covers alternatives for common use cases: platform serialization (use records, readResolve, or serialization proxy pattern), custom serialization libraries (prefer record-based protocols or proxy patterns), dependency injection (switch to constructor injection), and cloning (replace with copy constructors or static factory methods). The core advice is to embrace constructors as the single point of instance creation, since they properly assign final fields and enforce class invariants. The --enable-final-field-mutation flag exists as a last resort for cases with no other solution.

You Must Avoid Final Field Mutation - Inside Java Newscast #110