Explain the JVM architecture and class loading mechanism.

JVM components: Class Loader Subsystem (loads .class files), Runtime Data Areas (method area, heap, stack, PC registers, native method stack), Execution Engine (interpreter, JIT compiler, GC). Class loading: Bootstrap (core Java classes), Extension, Application loaders. Loading phases: load (read bytecode), link (verify, prepare, resolve), initialize (static blocks). Class loaders follow delegation model - child delegates to parent first. Custom class loaders enable: hot deployment, isolation, dynamic loading. JIT compiles hot code to native. Metaspace (Java 8+) replaces PermGen for class metadata.