The Java Version Almanac
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Java Bytecode

Constant

Push contant values to operand stack.

Mnemonic Opcode Description
aconst_null 1 Push null
bipush 16 Push byte
dconst_0 14 Push double value 0.0
dconst_1 15 Push double value 1.0
fconst_0 11 Push float value 0.0
fconst_1 12 Push float value 1.0
fconst_2 13 Push float value 2.0
iconst_0 3 Push int constant 0
iconst_1 4 Push int constant 1
iconst_2 5 Push int constant 2
iconst_3 6 Push int constant 3
iconst_4 7 Push int constant 4
iconst_5 8 Push int constant 5
iconst_m1 2 Push int constant -1
lconst_0 9 Push long constant
lconst_1 10 Push long constant
ldc 18 Push item from constant pool
ldc2_w 20 Push long or double from constant pool (wide index)
ldc_w 19 Push item from constant pool (wide index)
sipush 17 Push short
Data Source

Load

Load operand stack value from local variable.

Mnemonic Opcode Description
aload 25 Load reference from local variable
aload_0 42 Load reference from local variable 0
aload_1 43 Load reference from local variable 1
aload_2 44 Load reference from local variable 2
aload_3 45 Load reference from local variable 3
dload 24 Load double from local variable
dload_0 38 Load double from local variable 0
dload_1 39 Load double from local variable 1
dload_2 40 Load double from local variable 2
dload_3 41 Load double from local variable 3
fload 23 Load float from local variable
fload_0 34 Load float from local variable 0
fload_1 35 Load float from local variable 1
fload_2 36 Load float from local variable 2
fload_3 37 Load float from local variable 3
iload 21 Load int from local variable
iload_0 26 Load int from local variable
iload_1 27 Load int from local variable
iload_2 28 Load int from local variable
iload_3 29 Load int from local variable
lload 22 Load long from local variable
lload_0 30 Load long from local variable 0
lload_1 31 Load long from local variable 1
lload_2 32 Load long from local variable 2
lload_3 33 Load long from local variable 3
Data Source

Store

Store operand stack value to local variable.

Mnemonic Opcode Description
astore 58 Store reference into local variable
astore_0 75 Store reference into local variable 0
astore_1 76 Store reference into local variable 1
astore_2 77 Store reference into local variable 2
astore_3 78 Store reference into local variable 3
dstore 57 Store double into local variable
dstore_0 71 Store double into local variable 0
dstore_1 72 Store double into local variable 1
dstore_2 73 Store double into local variable 2
dstore_3 74 Store double into local variable 3
fstore 56 Store float into local variable
fstore_0 67 Store float into local variable 0
fstore_1 68 Store float into local variable 1
fstore_2 69 Store float into local variable 2
fstore_3 70 Store float into local variable 3
istore 54 Store int into local variable
istore_0 59 Store int into local variable 0
istore_1 60 Store int into local variable 1
istore_2 61 Store int into local variable 2
istore_3 62 Store int into local variable 3
lstore 55 Store long into local variable
lstore_0 63 Store long into local variable 0
lstore_1 64 Store long into local variable 1
lstore_2 65 Store long into local variable 2
lstore_3 66 Store long into local variable 3
Data Source

Stack

Manage operand stack.

Mnemonic Opcode Description
dup 89 Duplicate the top operand stack value
dup2 92 Duplicate the top one or two operand stack values
dup2_x1 93 Duplicate the top one or two operand stack values and insert two or three values down
dup2_x2 94 Duplicate the top one or two operand stack values and insert two, three, or four values down
dup_x1 90 Duplicate the top operand stack value and insert two values down
dup_x2 91 Duplicate the top operand stack value and insert two or three values down
pop 87 Pop the top operand stack value
pop2 88 Pop the top one or two operand stack values
swap 95 Swap the top two operand stack values
Data Source

Math

Calculate on operand stack.

Mnemonic Opcode Description
dadd 99 Add double
ddiv 111 Divide double
dmul 107 Multiply double
dneg 119 Negate double
drem 115 Remainder double
dsub 103 Subtract double
fadd 98 Add float
fdiv 110 Divide float
fmul 106 Multiply float
fneg 118 Negate float
frem 114 Remainder float
fsub 102 Subtract float
iadd 96 Add int
iand 126 Boolean AND int
idiv 108 Divide int
iinc 132 Increment local variable by constant
imul 104 Multiply int
ineg 116 Negate int
ior 128 Boolean OR int
irem 112 Remainder int
ishl 120 Shift left int
ishr 122 Arithmetic shift right int
isub 100 Subtract int
iushr 124 Logical shift right int
ixor 130 Boolean XOR int
ladd 97 Add long
land 127 Boolean AND long
ldiv 109 Divide long
lmul 105 Multiply long
lneg 117 Negate long
lor 129 Boolean OR long
lrem 113 Remainder long
lshl 121 Shift left long
lshr 123 Arithmetic shift right long
lsub 101 Subtract long
lushr 125 Logical shift right long
lxor 131 Boolean XOR long
Data Source

Conversion

Convert numeric types on operand stack.

Mnemonic Opcode Description
d2f 144 Convert double to float
d2i 142 Convert double to int
d2l 143 Convert double to long
f2d 141 Convert float to double
f2i 139 Convert float to int
f2l 140 Convert float to long
i2b 145 Convert int to byte
i2c 146 Convert int to char
i2d 135 Convert int to double
i2f 134 Convert int to float
i2l 133 Convert int to long
i2s 147 Convert int to short
l2d 138 Convert long to double
l2f 137 Convert long to float
l2i 136 Convert long to int
Data Source

Comparison

Compare values on operand stack.

Mnemonic Opcode Description
dcmpg 152 Compare double
dcmpl 151 Compare double
fcmpg 150 Compare float
fcmpl 149 Compare float
lcmp 148 Compare long
Data Source

Conditional

Conditional jumps depending on values on operand stack.

Mnemonic Opcode Description
if_acmpeq 165 Jump if reference comparison succeeds
if_acmpne 166 Jump if reference comparison succeeds
if_icmpeq 159 Jump if int comparison succeeds
if_icmpge 162 Jump if int comparison succeeds
if_icmpgt 163 Jump if int comparison succeeds
if_icmple 164 Jump if int comparison succeeds
if_icmplt 161 Jump if int comparison succeeds
if_icmpne 160 Jump if int comparison succeeds
ifeq 153 Jump if int comparison with zero succeeds
ifge 156 Jump if int comparison with zero succeeds
ifgt 157 Jump if int comparison with zero succeeds
ifle 158 Jump if int comparison with zero succeeds
iflt 155 Jump if int comparison with zero succeeds
ifne 154 Jump if int comparison with zero succeeds
ifnonnull 199 Jump if reference not null
ifnull 198 Jump if reference is null
lookupswitch 171 Access jump table by key match and jump
tableswitch 170 Access jump table by index and jump
Data Source

Objects

Interact with objects.

Mnemonic Opcode Description
checkcast 192 Check whether reference is of given type
getfield 180 Fetch field from object
getstatic 178 Get static field from class
instanceof 193 Determine if reference is of given type
invokedynamic 186 Invoke a dynamically-computed call site
invokeinterface 185 Invoke interface method
invokespecial 183 Directly invoke instance (initialization) method of the current class or its supertypes
invokestatic 184 Invoke static method
invokevirtual 182 Invoke instance method, dispatch based on class
new 187 Create new object
putfield 181 Set field in object
putstatic 179 Set static field in class
Data Source

Array

Create and access arrays.

Mnemonic Opcode Description
aaload 50 Load reference from array
aastore 83 Store into reference array
anewarray 189 Create new array of reference
arraylength 190 Get length of array
baload 51 Load byte or boolean from array
bastore 84 Store into byte or boolean array
caload 52 Load char from array
castore 85 Store into char array
daload 49 Load double from array
dastore 82 Store into double array
faload 48 Load float from array
fastore 81 Store into float array
iaload 46 Load int from array
iastore 79 Store into int array
laload 47 Load long from array
lastore 80 Store into long array
multianewarray 197 Create new multidimensional array
newarray 188 Create new array
saload 53 Load short from array
sastore 86 Store into short array
Data Source

Control Flow

Manage the control flow.

Mnemonic Opcode Description
areturn 176 Return reference from method
athrow 191 Throw Throwable reference
dreturn 175 Return double from method
freturn 174 Return float from method
goto 167 Unconditional jump
goto_w 200 Unconditional jump (wide index)
ireturn 172 Return int from method
jsr 168 Jump subroutine
jsr_w 201 Jump subroutine (wide index)
lreturn 173 Return long from method
ret 169 Return from subroutine
return 177 Return void from method
Data Source

Other

Various uncategorized opcodes

Mnemonic Opcode Description
monitorenter 194 Enter monitor for object
monitorexit 195 Exit monitor for object
nop 0 Do nothing
wide 196 Extend local variable index by additional bytes
Data Source

Reserved

Reserved opcodes for internal usage in VM implementations only.

Mnemonic Opcode Description
breakpoint 202 Reserved for internal usage in debuggers
impdep1 254 Reserved for internal usage in JVM
impdep2 255 Reserved for internal usage in JVM
Data Source