JDK 26: Final Will Actually Mean Final Now

Did you know Java reflection can mutate private final fields? That's about to change. JDK 26 introduces JEP 500: Prepare to Make Final Mean Final, and it's the first step toward locking down final fields for good. In this video, I walk you through JEP 500 from JDK 26, fresh from the Java One conference in Redwood Shores, California. We'll build a simple project from scratch to see how reflection can currently modify final fields in JDK 25, then switch to JDK 26 to explore the new warning, debug, and deny modes that prepare developers for a future where final truly means final. - How Java reflection can be used to mutate private final fields (and why that's a problem) - What JEP 500 does in JDK 26: warnings for final field mutation via reflection - The three modes: warn (default), debug (with stack traces), and deny (blocks mutation entirely) - How to configure the --illegal-final-field-mutation flag in your projects - Understanding Java's Integrity by Default roadmap and what's coming in future JDK releases If you learned something new about JDK 26 today, leave a thumbs up, subscribe to the channel, and let me know in the comments which JDK 26 feature you'd like me to cover next! 0:00 - Intro & Java One Recap 0:40 - JDK 26 Overview & JEP 500 Introduction 1:30 - What Does "Final Means Final" Mean? 2:20 - Creating the Project in IntelliJ (JDK 25) 3:15 - Building the Person Class with a Final Field 4:30 - Mutating a Final Field Using Reflection 5:40 - Running on JDK 25 — It Works (Yikes!) 6:10 - Switching to JDK 26 & Maven Configuration 7:00 - Warn Mode (Default) — New JDK 26 Warnings 8:00 - Debug Mode — Extra Stack Trace Info 8:30 - Deny Mode — Mutation Blocked Completely 9:10 - Recap & What's Coming in Future JDKs 9:50 - Java One Highlights & Wrap Up 🔗Resources & Links mentioned in this video: GitHub Repository — Final Means Final Demo: https://github.com/danvega/final-means-final JEP 500: Prepare to Make Final Mean Final: https://openjdk.org/jeps/500 JDK 26 Re