Teach Yourself Java in 21 Days

Day

21

Under the Hood

421

The Big Picture ...................................................................................... 422

Why It’s a Powerful Vision ................................................................ 423

The Java Virtual Machine ....................................................................... 423

An Overview ...................................................................................... 424

The Fundamental Parts ...................................................................... 426

The Constant Pool ............................................................................ 430

Limitations ........................................................................................ 430

Bytecodes in More Detail ....................................................................... 431

The Bytecode Interpreter ................................................................... 431

The “Just-in-Time” Compiler ............................................................ 432

The java2c Translator ........................................................................ 433

The Bytecodes Themselves ................................................................ 434

The _quick Bytecodes ........................................................................ 450

The .class File Format ............................................................................. 452

Method Signatures ................................................................................. 454

The Garbage Collector ........................................................................... 455

The Problem ...................................................................................... 455

The Solution ...................................................................................... 456

Java’s Parallel Garbage Collector ........................................................ 459

The Security Story .................................................................................. 459

Why You Should Worry .................................................................... 459

Why You Might Not Have To .......................................................... 460

Java’s Security Model ......................................................................... 460

Summary ................................................................................................ 470

Q&A ...................................................................................................... 470