Teach Yourself Java in 21 Days

Native Methods and Libraries
403
Disadvantages of native Methods ............................................................ 404
The Illusion of Required Efficiency ........................................................ 405
Built-In Optimizations ...................................................................... 407
Simple Optimization Tricks............................................................... 407
Writing native Methods .......................................................................... 408
The Example Class ............................................................................ 409
Generating Header and Stub Files ..................................................... 410
Creating SimpleFileNative.c .............................................................. 414
030-4 FM
1/29/96, 8:11 PM
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P2/V4SQC6 TY Java in 21 Days 030-4 louisa 12.31.95
FM LP#4
A Native Library ..................................................................................... 417
Linking It All ..................................................................................... 418
Using Your Library ............................................................................ 418
Summary ................................................................................................ 418
Q&A ...................................................................................................... 419
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