The Java® Virtual Machine Specification

Java SE 16 Edition

Tim Lindholm

Frank Yellin

Gilad Bracha

Alex Buckley

Daniel Smith

2021-02-12

Legal Notice

Table of Contents

1. Introduction
1.1. A Bit of History
1.2. The Java Virtual Machine
1.3. Organization of the Specification
1.4. Notation
1.5. Feedback
2. The Structure of the Java Virtual Machine
2.1. The class File Format
2.2. Data Types
2.3. Primitive Types and Values
2.3.1. Integral Types and Values
2.3.2. Floating-Point Types, Value Sets, and Values
2.3.3. The returnAddress Type and Values
2.3.4. The boolean Type
2.4. Reference Types and Values
2.5. Run-Time Data Areas
2.5.1. The pc Register
2.5.2. Java Virtual Machine Stacks
2.5.3. Heap
2.5.4. Method Area
2.5.5. Run-Time Constant Pool
2.5.6. Native Method Stacks
2.6. Frames
2.6.1. Local Variables
2.6.2. Operand Stacks
2.6.3. Dynamic Linking
2.6.4. Normal Method Invocation Completion
2.6.5. Abrupt Method Invocation Completion
2.7. Representation of Objects
2.8. Floating-Point Arithmetic
2.8.1. Java Virtual Machine Floating-Point Arithmetic and IEEE 754
2.8.2. Floating-Point Modes
2.8.3. Value Set Conversion
2.9. Special Methods
2.9.1. Instance Initialization Methods
2.9.2. Class Initialization Methods
2.9.3. Signature Polymorphic Methods
2.10. Exceptions
2.11. Instruction Set Summary
2.11.1. Types and the Java Virtual Machine
2.11.2. Load and Store Instructions
2.11.3. Arithmetic Instructions
2.11.4. Type Conversion Instructions
2.11.5. Object Creation and Manipulation
2.11.6. Operand Stack Management Instructions
2.11.7. Control Transfer Instructions
2.11.8. Method Invocation and Return Instructions
2.11.9. Throwing Exceptions
2.11.10. Synchronization
2.12. Class Libraries
2.13. Public Design, Private Implementation
3. Compiling for the Java Virtual Machine
3.1. Format of Examples
3.2. Use of Constants, Local Variables, and Control Constructs
3.3. Arithmetic
3.4. Accessing the Run-Time Constant Pool
3.5. More Control Examples
3.6. Receiving Arguments
3.7. Invoking Methods
3.8. Working with Class Instances
3.9. Arrays
3.10. Compiling Switches
3.11. Operations on the Operand Stack
3.12. Throwing and Handling Exceptions
3.13. Compiling finally
3.14. Synchronization
3.15. Annotations
3.16. Modules
4. The class File Format
4.1. The ClassFile Structure
4.2. Names
4.2.1. Binary Class and Interface Names
4.2.2. Unqualified Names
4.2.3. Module and Package Names
4.3. Descriptors
4.3.1. Grammar Notation
4.3.2. Field Descriptors
4.3.3. Method Descriptors
4.4. The Constant Pool
4.4.1. The CONSTANT_Class_info Structure
4.4.2. The CONSTANT_Fieldref_info, CONSTANT_Methodref_info, and CONSTANT_InterfaceMethodref_info Structures
4.4.3. The CONSTANT_String_info Structure
4.4.4. The CONSTANT_Integer_info and CONSTANT_Float_info Structures
4.4.5. The CONSTANT_Long_info and CONSTANT_Double_info Structures
4.4.6. The CONSTANT_NameAndType_info Structure
4.4.7. The CONSTANT_Utf8_info Structure
4.4.8. The CONSTANT_MethodHandle_info Structure
4.4.9. The CONSTANT_MethodType_info Structure
4.4.10. The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
4.4.11. The CONSTANT_Module_info Structure
4.4.12. The CONSTANT_Package_info Structure
4.5. Fields
4.6. Methods
4.7. Attributes
4.7.1. Defining and Naming New Attributes
4.7.2. The ConstantValue Attribute
4.7.3. The Code Attribute
4.7.4. The StackMapTable Attribute
4.7.5. The Exceptions Attribute
4.7.6. The InnerClasses Attribute
4.7.7. The EnclosingMethod Attribute
4.7.8. The Synthetic Attribute
4.7.9. The Signature Attribute
4.7.9.1. Signatures
4.7.10. The SourceFile Attribute
4.7.11. The SourceDebugExtension Attribute
4.7.12. The LineNumberTable Attribute
4.7.13. The LocalVariableTable Attribute
4.7.14. The LocalVariableTypeTable Attribute
4.7.15. The Deprecated Attribute
4.7.16. The RuntimeVisibleAnnotations Attribute
4.7.16.1. The element_value structure
4.7.17. The RuntimeInvisibleAnnotations Attribute
4.7.18. The RuntimeVisibleParameterAnnotations Attribute
4.7.19. The RuntimeInvisibleParameterAnnotations Attribute
4.7.20. The RuntimeVisibleTypeAnnotations Attribute
4.7.20.1. The target_info union
4.7.20.2. The type_path structure
4.7.21. The RuntimeInvisibleTypeAnnotations Attribute
4.7.22. The AnnotationDefault Attribute
4.7.23. The BootstrapMethods Attribute
4.7.24. The MethodParameters Attribute
4.7.25. The Module Attribute
4.7.26. The ModulePackages Attribute
4.7.27. The ModuleMainClass Attribute
4.7.28. The NestHost Attribute
4.7.29. The NestMembers Attribute
4.7.30. The Record Attribute
4.8. Format Checking
4.9. Constraints on Java Virtual Machine Code
4.9.1. Static Constraints
4.9.2. Structural Constraints
4.10. Verification of class Files
4.10.1. Verification by Type Checking
4.10.1.1. Accessors for Java Virtual Machine Artifacts
4.10.1.2. Verification Type System
4.10.1.3. Instruction Representation
4.10.1.4. Stack Map Frames and Type Transitions
4.10.1.5. Type Checking Abstract and Native Methods
4.10.1.6. Type Checking Methods with Code
4.10.1.7. Type Checking Load and Store Instructions
4.10.1.8. Type Checking for protected Members
4.10.1.9. Type Checking Instructions
aaload
aastore
aconst_null
aload, aload_<n>
anewarray
areturn
arraylength
astore, astore_<n>
athrow
baload
bastore
bipush
caload
castore
checkcast
d2f, d2i, d2l
dadd
daload
dastore
dcmp<op>
dconst_<d>
ddiv
dload, dload_<n>
dmul
dneg
drem
dreturn
dstore, dstore_<n>
dsub
dup
dup_x1
dup_x2
dup2
dup2_x1
dup2_x2
f2d, f2i, f2l
fadd
faload
fastore
fcmp<op>
fconst_<f>
fdiv
fload, fload_<n>
fmul
fneg
frem
freturn
fstore, fstore_<n>
fsub
getfield
getstatic
goto, goto_w
i2b, i2c, i2d, i2f, i2l, i2s
iadd
iaload
iand
iastore
iconst_<i>
idiv
if_acmp<cond>
if_icmp<cond>
if<cond>
ifnonnull, ifnull
iinc
iload, iload_<n>
imul
ineg
instanceof
invokedynamic
invokeinterface
invokespecial
invokestatic
invokevirtual
ior, irem
ireturn
ishl, ishr, iushr
istore, istore_<n>
isub, ixor
l2d, l2f, l2i
ladd
laload
land
lastore
lcmp
lconst_<l>
ldc, ldc_w, ldc2_w
ldiv
lload, lload_<n>
lmul
lneg
lookupswitch
lor, lrem
lreturn
lshl, lshr, lushr
lstore, lstore_<n>
lsub, lxor
monitorenter, monitorexit
multianewarray
new
newarray
nop
pop, pop2
putfield
putstatic
return
saload
sastore
sipush
swap
tableswitch
wide
4.10.2. Verification by Type Inference
4.10.2.1. The Process of Verification by Type Inference
4.10.2.2. The Bytecode Verifier
4.10.2.3. Values of Types long and double
4.10.2.4. Instance Initialization Methods and Newly Created Objects
4.10.2.5. Exceptions and finally
4.11. Limitations of the Java Virtual Machine
5. Loading, Linking, and Initializing
5.1. The Run-Time Constant Pool
5.2. Java Virtual Machine Startup
5.3. Creation and Loading
5.3.1. Loading Using the Bootstrap Class Loader
5.3.2. Loading Using a User-defined Class Loader
5.3.3. Creating Array Classes
5.3.4. Loading Constraints
5.3.5. Deriving a Class from a class File Representation
5.3.6. Modules and Layers
5.4. Linking
5.4.1. Verification
5.4.2. Preparation
5.4.3. Resolution
5.4.3.1. Class and Interface Resolution
5.4.3.2. Field Resolution
5.4.3.3. Method Resolution
5.4.3.4. Interface Method Resolution
5.4.3.5. Method Type and Method Handle Resolution
5.4.3.6. Dynamically-Computed Constant and Call Site Resolution
5.4.4. Access Control
5.4.5. Method Overriding
5.4.6. Method Selection
5.5. Initialization
5.6. Binding Native Method Implementations
5.7. Java Virtual Machine Exit
6. The Java Virtual Machine Instruction Set
6.1. Assumptions: The Meaning of "Must"
6.2. Reserved Opcodes
6.3. Virtual Machine Errors
6.4. Format of Instruction Descriptions
mnemonic
6.5. Instructions
aaload
aastore
aconst_null
aload
aload_<n>
anewarray
areturn
arraylength
astore
astore_<n>
athrow
baload
bastore
bipush
caload
castore
checkcast
d2f
d2i
d2l
dadd
daload
dastore
dcmp<op>
dconst_<d>
ddiv
dload
dload_<n>
dmul
dneg
drem
dreturn
dstore
dstore_<n>
dsub
dup
dup_x1
dup_x2
dup2
dup2_x1
dup2_x2
f2d
f2i
f2l
fadd
faload
fastore
fcmp<op>
fconst_<f>
fdiv
fload
fload_<n>
fmul
fneg
frem
freturn
fstore
fstore_<n>
fsub
getfield
getstatic
goto
goto_w
i2b
i2c
i2d
i2f
i2l
i2s
iadd
iaload
iand
iastore
iconst_<i>
idiv
if_acmp<cond>
if_icmp<cond>
if<cond>
ifnonnull
ifnull
iinc
iload
iload_<n>
imul
ineg
instanceof
invokedynamic
invokeinterface
invokespecial
invokestatic
invokevirtual
ior
irem
ireturn
ishl
ishr
istore
istore_<n>
isub
iushr
ixor
jsr
jsr_w
l2d
l2f
l2i
ladd
laload
land
lastore
lcmp
lconst_<l>
ldc
ldc_w
ldc2_w
ldiv
lload
lload_<n>
lmul
lneg
lookupswitch
lor
lrem
lreturn
lshl
lshr
lstore
lstore_<n>
lsub
lushr
lxor
monitorenter
monitorexit
multianewarray
new
newarray
nop
pop
pop2
putfield
putstatic
ret
return
saload
sastore
sipush
swap
tableswitch
wide
7. Opcode Mnemonics by Opcode
A. Limited License Grant