The nucleus of the Java(TM) 2 platform, the Java(TM) virtual machine is the technology that enables the Java 2 platform to host applications on any computer or operating system without rewriting or recompiling. The Java virtual machine is also responsible for the compactness of applications targeting the Java 2 platform, and is the basis for its security capabilities.

This book was written by those directly responsible for the design and implementation of the Java virtual machine, and is the complete and definitive specification for the technology. It is an essential reference for writers of compilers for the Java programming language and implementors of the Java virtual machine. This second edition specifies the newest version of the Java virtual machine and provides a fascinating view into the inner workings of the Java 2 platform.

In this book you will find comprehensive coverage of the class file format, the hardware, operating system, and implementation-independent binary format for compiled code. The authors fully describe the instruction set of the Java virtual machine. You will find an entire chapter of examples that demonstrate how to compile code written in the Java programming language into the instruction set of the Java virtual machine. In addition, the book presents a discussion on the vital topic of Java virtual machine threads and their interaction with memory.

All in all, this comprehensive, detailed, and methodical presentation provides the information necessary to implement your own fully compatible Java virtual machine.

0201432943B04062001

Tim Lindholm, Distinguished Engineer in Java Software at Sun Microsystems, Inc., was an original member of the Java project at Sun. He was a key contributor to the Java programming language and remains the senior architect of the Java virtual machine and the Java 2 runtime environment. He is also the Technical Editor of The Java(TM) Series.

Frank Yellin, Staff Engineer in Embedded and Consumer at Sun Microsystems, Inc., was an original member of the Java project at Sun. He has spent a decade working on the runtime systems for interpreted and compiled languages. Previously he worked at Lucid, where he focused on multitasking, garbage collection, interrupts, and the compilation of Common Lisp.

0201432943AB04062001

Preface

xiii

Introduction

1

(4)

A Bit of History

1

(1)

The Java Virtual Machine

2

(1)

Summary of Chapters

3

(1)

Notation

3

(2)

Java Programming Language Concepts

5

(56)

Unicode

5

(1)

Identifiers

6

(1)

Literals

6

(1)

Types and Values

7

(6)

Primitive Types and Values

7

(1)

Operators on Integral Values

8

(1)

Floating-Point Types, Value Sets, and Values

8

(2)

Operators on Floating-Point Values

10

(1)

Operators on boolean Values

11

(1)

Reference Types, Objects, and Reference Values

11

(1)

The Class Object

12

(1)

The Class String

12

(1)

Operators on Objects

12

(1)

Variables

13

(3)

Initial Values of Variables

14

(1)

Variables Have Types, Objects Have Classes

15

(1)

Conversions and Promotions

16

(8)

Identity Conversions

17

(1)

Widening Primitive Conversions

17

(1)

Narrowing Primitive Conversions

18

(1)

Widening Reference Conversions

19

(1)

Narrowing Reference Conversions

19

(1)

Value Set Conversion

20

(1)

Assignment Conversion

21

(1)

Method Invocation Conversion

22

(1)

Casting Conversion

23

(1)

Numeric Promotion

23

(1)

Names and Packages

24

(4)

Simple Names and Qualified Names

24

(1)

Packages

24

(1)

Members

25

(1)

Qualified Names and Access Control

26

(1)

Fully Qualified Names

27

(1)

Classes

28

(1)

Class Names

28

(1)

Class Modifiers

28

(1)

Superclasses and Subclasses

29

(1)

The Class Members

29

(1)

Fields

29

(2)

Field Modifiers

30

(1)

Initialization of Fields

31

(1)

Methods

31

(2)

Formal Parameters

32

(1)

Method Signature

32

(1)

Method Modifiers

32

(1)

Static Initializers

33

(1)

Constructors

34

(1)

Constructor Modifiers

34

(1)

Interfaces

35

(2)

Interface Modifiers

35

(1)

Superinterfaces

36

(1)

Interfaces Members

36

(1)

Overriding, Inheritance, and Overloading in Interfaces

37

(1)

Nested Classes and Interfaces

37

(1)

Arrays

38

(1)

Array Types

38

(1)

Array Variables

39

(1)

Array Creation

39

(1)

Array Access

39

(1)

Exceptions

39

(7)

The Causes of Exceptions

40

(1)

Handling an Exception

41

(2)

The Exception Hierarchy

43

(1)

The Classes Exception and RuntimeException

43

(3)

Execution

46

(11)

Virtual Machine Start-up

46

(2)

Loading

48

(1)

Linking: Verification, Preparation, and Resolution

49

(2)

Initialization

51

(1)

Detailed Initialization Procedure

52

(2)

Creation of New Class Instances

54

(2)

Finalization of Class Instances

56

(1)

Unloading of Classes and Interfaces

57

(1)

Virtual Machine Exit

57

(1)

FP-strict Expressions

57

(1)

Threads

58

(3)

The Structure of the Java Virtual Machine

61

(32)

The Class File Format

61

(1)

Data Types

61

(1)

Primitive Types and Values

62

(4)

Integral Types and Values

63

(1)

Floating-Point Types, Value Sets, and Values

63

(3)

The returnAddress Types and Values

66

(1)

The boolean Type

66

(1)

Reference Types and Values

66

(1)

Runtime Data Areas

67

(4)

The pc Register

67

(1)

Java Virtual Machine Stacks

67

(1)

Heap

68

(1)

Method Area

69

(1)

Runtime Constant Pool

70

(1)

Native Method Stacks

70

(1)

Frames

71

(4)

Local Variables

72

(1)

Operand Stacks

73

(1)

Dynamic Linking

74

(1)

Normal Method Invocation Completion

74

(1)

Abrupt Method Invocation Completion

74

(1)

Additional Information

75

(1)

Representation of Objects

75

(1)

Floating-Point Arithmetic

75

(3)

Java Virtual Machine Floating-Point Arithmetic and IEEE 754

75

(1)

Floating-Point Modes

76

(1)

Value Set Conversion

77

(1)

Specially Named Initialization Methods

78

(1)

Exceptions

78

(2)

Instruction Set Summary

80

(11)

Types and the Java Virtual Machine

80

(3)

Load and Store Instructions

83

(1)

Arthmetic Instructions

84

(2)

Type Conversion Instructions

86

(2)

Object Creation and Manipulation

88

(1)

Operand Stack Management Instructions

88

(1)

Control Transfer Instructions

88

(1)

Method Invocation and Return Instructions

89

(1)

Throwing Exceptions

90

(1)

Implementing finally

90

(1)

Synchronization

90

(1)

Class Libraries

91

(1)

Public Design, Private Implementation

91

(2)

The Class File Format

93

(62)

The ClassFile Structure

94

(5)

The Internal Form of Fully Qualified Class and Interface Names

99

(1)

Descriptors

99

(4)

Grammar Notation

99

(1)

Field Descriptors

100

(2)

Method Descriptors

102

(1)

The Constant Pool

103

(9)

The CONSTANT_Class_info Structure

104

(1)

The CONSTANT_Fieldref_info, CONSTANT_Methodref_info, and CONSTANT_InterfaceMethodref_info Structures

105

(1)

The CONSTANT_String_info Structure

106

(1)

The CONSTANT_Integer_info and CONSTANT_Float_info Structures

107

(1)

The CONSTANT_Long_info and CONSTANT_Double_info Structures

108

(2)

The CONSTANT_NameAndType_info Structure

110

(1)

The CONSTANT_Utf8_info Structure

110

(2)

Fields

112

(2)

Methods

114

(3)

Attributes

117

(16)

Defining and Naming New Attributes

118

(1)

The ConstantValue Attribute

119

(1)

The Code Attribute

120

(3)

The Exceptions Attribute

123

(2)

The InnerClasses Attribute

125

(2)

The Synthetic Attribute

127

(1)

The SourceFile Attribute

128

(1)

The LineNumberTable Attribute

129

(1)

The LocalVariableTable Attribute

130

(2)

The Deprecated Attribute

132

(1)

Constraints on Java Virtual Machine Code

133

(7)

Static Constraints

133

(4)

Structural Constraints

137

(3)

Verification of class Files

140

(12)

The Verification Process

141

(2)

The Bytecode Verifier

143

(3)

Values of Types long and double

146

(1)

Instance Initialization Methods and Newly Created Objects

147

(1)

Exception Handlers

148

(1)

Exceptions and finally

149

(3)

Limitations of the Java Virtual Machine

152

(3)

Loading, Linking, and Initializing

155

(16)

The Runtime Constant Pool

155

(3)

Virtual Machine Start-up

158

(1)

Creation and Loading

158

(6)

Loading Using the Bootstrap Class Loader

160

(1)

Loading Using a User-defined Class Loader

160

(1)

Creating Array Classes

161

(1)

Loading Constraints

162

(1)

Deriving a Class from a class File Representation

163

(1)

Linking

164

(6)

Verification

164

(1)

Preparation

165

(1)

Resolution

165

(4)

Access Control

169

(1)

Initialization

170

(1)

Binding Native Method Implementations

170

(1)

The Java Virtual Machine Instruction Set

171

(192)

Assumptions: The Meaning of ``Most''

171

(1)

Reserved Opcodes

172

(1)

Virtual Machine Errors

172

(1)

Format of Instruction Descriptions

172

(191)

Compiling for the Java Virtual Machine

363

(34)

Format of Examples

364

(1)

Use of Constants, Local Variables, and Control Constructs

365

(4)

Arithmetic

369

(1)

Accessing the Runtime Constant Pool

370

(2)

More Control Examples

372

(3)

Receiving Arguments

375

(1)

Invoking Methods

376

(3)

Working with Class Instances

379

(2)

Arrays

381

(3)

Compiling Switches

384

(2)

Operations on the Operand Stack

386

(1)

Throwing and Handling Exceptions

387

(4)

Compiling finally

391

(3)

Synchronization

394

(2)

Compiling Nested Classes and Interfaces

396

(1)

Threads and Locks

397

(18)

Terminology and Framework

397

(2)

Execution Order and Consistency

399

(1)

Rules About Variables

400

(2)

Nonatomic Treatment of double and long Variables

402

(1)

Rules About Locks

402

(1)

Rules About the Interaction of Locks and Variables

403

(1)

Rules for volatile Variables

404

(1)

Prescient Store Operations

404

(1)

Discussion

405

(1)

Example: Possible Swap

406

(4)

Example: Out-of-Order Writes

410

(2)

Threads

412

(1)

Locks and Synchronization

412

(1)

Wait Sets and Notification

413

(2)

Opcode Mnemonics by Opcode

415

(4)

Appendix: Summary of Clarifications and Amendments

419

(12)

Index

431

What is included with this book?

The New copy of this book will include any supplemental materials advertised. Please check the title of the book to determine if it should include any access cards, study guides, lab manuals, CDs, etc.

The Used, Rental and eBook copies of this book are not guaranteed to include any supplemental materials. Typically, only the book itself is included. This is true even if the title states it includes any access cards, study guides, lab manuals, CDs, etc.

The Java(TM) virtual machine specification has been written to fully document the design of the Java virtual machine. It is essential for compiler writers who wish to target the Java virtual machine and for programmers who want to implement a compatible Java virtual machine. It is also a definitive source for anyone who wants to know exactly how the Java programming language is implemented. The Java virtual machine is an abstract machine. References to the Java virtual machinethroughout this specification refer to this abstract machine rather than to Sun''s or any other specific implementation. This book serves as documentation for a concrete implementation of the Java virtual machine only as a blueprint documents a house. An implementation of the Java virtual machine (known as a runtime interpreter) must embody this specification, but is constrained by it only where absolutely necessary. The Java virtual machine specified here will support the Java programming language specified in The Java(TM) Language Specification(Addison-Wesley, 1996). It is compatible with the Java platform implemented by Sun''s JDK(TM) releases 1.0.2 and 1.1 and the Java(R) 2 platform implemented by Sun''s Java(R) 2 SDK, Standard Edition, v1.2 (formerly known as JDK release 1.2). We intend that this specification should sufficiently document the Java virtual machine to make possible compatible clean-room implementations. If you are considering constructing your own Java virtual machine implementation, feel free to contact us to obtain assistance to ensure the 100% compatibility of your implementation. Send comments on this specification or questions about implementing the Java virtual machine to our electronic mail address:jvm@java.sun.com. To learn the latest about the Java 2 platform, or to download the latest Java 2 SDK release, visit our World Wide Web site athttp://java.sun.com. For updated information about the Java Series, including errata for The Java(TM) Virtual Machine Specification, and previews of forthcoming books, visithttp://java.sun.com/Series The virtual machine that evolved into the Java virtual machine was originally designed by James Gosling in 1992 to support the Oak programming language. The evolution into its present form occurred through the direct and indirect efforts of many people and spanned Sun''s Green project, FirstPerson, Inc., the LiveOak project, the Java Products Group, JavaSoft, and today, Sun''s Java Software. The authors are grateful to the many contributors and supporters. This book began as internal project documentation. Kathy Walrath edited that early draft, helping to give the world its first look at the internals of the Java programming language. It was then converted to HTML by Mary Campione and was made available on our Web site before being expanded into book form. The creation of The Java(TM) Virtual Machine Specificationowes much to the support of the Java Products Group led by General Manager Ruth Hennigar, to the efforts of series editor Lisa Friendly, and to editor Mike Hendrickson and his group at Addison-Wesley. The many criticisms and suggestions received from reviewers of early online drafts, as well as drafts of the printed book, improved its quality immensely. We owe special thanks to Richard Tuck for his careful review of the manuscript and to the authors of The Java(TM) Language Specification,Addison-Wesley, 1996, for allowing us to quote extensively from that book. Particular thanks to Bill Joy whose comments, reviews, and guidance have contributed greatly to the completeness and accuracy of this book. Notes on the Second Edition The second edition of The Java(TM) Virtual Machine Specificationbrings the specification of the Java virtual machine up to date with the Java(R) 2 platform, v1.2. It also includes many corrections and clarifications that update the presentation of the specification without changing the logical specification itself. We have attempted to correct typos and errata (hopefully without introducing new ones) and to add more detail to the specification where it was vague or ambiguous. In particular, we corrected a number of inconsistencies between the first edition of The Java(TM) Virtual Machine Specificationand The Java(TM) Language Specification. We thank the many readers who combed through the first edition of this book and brought problems to our attention. Several individuals and groups deserve special thanks for pointing out problems or contributing directly to the new material: Carla Schroer and her teams of compatibility testers in Cupertino, California, and Novosibirsk, Russia (with special thanks to Leonid Arbouzov and Alexei Kaigorodov), painstakingly wrote compatibility tests for each testable assertion in the first edition. In the process they uncovered many places where the original specification was unclear or incomplete. Jeroen Vermeulen, Janice Shepherd, Peter Bertelsen, Roly Perera, Joe Darcy, and Sandra Loosemore have all contributed comments and feedback that have improved this edition. Marilyn Rash and Hilary Selby Polk of Addison Wesley Longman helped us to improve the readability and layout of this edition at the same time as we were incorporating all the technical changes. Special thanks go to Gilad Bracha, who has brought a new level of rigor to the presentation and has been a major contributor to much of the new material, especially chapters 4 and 5 and the new "Appendix: Summary of Clarifications and Amendments." His dedication to "computational theology" and his commitment to resolving inconsistencies between The Java(TM) Virtual Machine Specificationand The Java(TM) Language Specificationhave benefited this book tremendously. Tim Lindholm Frank Yellin Java Software, Sun Microsystems, Inc. References --IEEE Standard for Binary Floating-Point Arithmetic,ANSI/IEEE Std. 754-1985. Available from Global Engineering Documents, 15 Inverness Way East, Englewood, Colorado 80112-5704 USA, +1 800 854 7179. --Hoare, C.A.R. Hints on Programming Language Design.Stanford University Computer Science Department Technical Report No CS-73-403, December 1973. Reprinted in Sigact/Sigplan Symposium on Principles of Programming Languages. Association for Computing Machinery, New York, October 1973. --Unicode Consortium, The. The Unicode Standard: Worldwide Character Encoding, Version 1.0, Volume 1,ISBN 0-201-56788-1, and Volume 2,ISBN 0-201-60845-6. Updates and additions necessary to bring the Unicode Standard up to version 1.1 may be found athttp://www.unicode.org--Unicode Consortium, The. The Unicode Standard, Version 2.0,ISBN 0-201-48345-9. Updates and additions necessary to bring the Unicode Standard up to version 2.1 may be found athttp://www.unicode.org 0201432943P04062001