Just a Small Class File Change - Nestmates and Access Control Evolution

Explore the process of implementing Nestmates, a feature for nested class access in Java, from concept to production. Dive into design considerations, specification changes, and implementation challenges. Learn about class file attributes, access control modifications, and the "Alternate Accessors" concept. Discover the impact of this seemingly small change on bytecode and classfiles. Gain insights into future developments for Nestmates, including sealed classes and the evolution of unsafe.DefineAnonymousClass. Understand the complexities involved in Java language and JVM specification updates through this comprehensive walkthrough.

Syllabus

Intro
Example: Nested Class Trampolines
Proposal: Nestmates
Just a Small Class File Change
JVMS Draft: Class File Attributes
JVMS Member Access Controls (Java SE 10)
Member Access Check: Java SE 10
Member Access Check: Nestmates
Proof of Concept: Implement and Test
Design Areas
Class File Attributes Implementation Challenges
JVMS Details: Class File Attributes
Access Controls Implementation Challenges
JVMS 5.4.4 Access Control Changes
JVMS 5.4.4 Nestmate Test
Alternate Accessors
Method Invocation
JVMS Method Selection Update
Production Quality
Additional Specification & Javadoc Changes
Production Level Implementation
Class File Readers and Writers
Test Creation
Nestmates Futures: Problems
Lookup.defineClass() Evolution
Dynamic Nestmates
Non-Findable Classes
Unsafe::defineAnonymousClass() Migration
Alternative to Constant Pool Patching
Questions