JDK 26: Warnings About Final Field Mutation – Inside.java

JDK 26 introduces warnings when final fields are mutated through Java's reflection API, as part of a broader effort to enforce integrity by default. The change is driven by JEP 500 and follows a pattern of Java progressively restricting capabilities that undermine language guarantees. Two new command-line options are introduced: `--enable-final-field-mutation` for permanent per-module permission, and `--illegal-final-field-mutation` for transitional control. Currently a warning, this will become an error in a future release. Library and framework maintainers are urged to stop relying on reflective final field mutation and adopt alternative approaches.