Explain JVM architecture and components (Class Loader, Runtime Data Areas, Execution Engine).

1. Class Loader Subsystem

• Loading: BootStrap, Extension, and Application ClassLoaders.
• Linking: Verify, Prepare, Resolve.
• Initialization: Static variables assigned original values.

2. Runtime Data Areas

• Method Area / Metaspace: Class-level data (Global).
• Heap Area: Objects and instance variables (Global).
• Stack Area: Method calls and local variables (Thread-specific).
• PC Registers: Address of current instruction (Thread-specific).
• Native Method Stack: Native function calls (Thread-specific).

3. Execution Engine

• Interpreter: Reads bytecode and executes.
• JIT Compiler: Compiles high-frequency bytecode to native machine code.
• Garbage Collector: Reclaims heap memory.