类加载

The class lifecycle: loading, linking, initialization, use, unloading, class loaders, parent delegation, and related questions.

When initialization is triggered, initialization rules, and examples for a single class and an inheritance hierarchy.

When a custom class loader is needed, how to implement one with findClass or loadClass, an example, and a reference.

Code, bytecode, explanation, and a proposed solution for object-creation instruction reordering.

Object composition, object headers, instance data, padding, and a JOL experiment.

Oracle JDK and OpenJDK use direct pointers: fast access, but pointers need to be updated if GC moves surviving objects.