Java bytecode instruction listings

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Main article: Java bytecode

This is a list of the instructions that make up the Java bytecode, an abstract machine language that is ultimately executed by the Java virtual machine. The Java bytecode is generated by language compilers targeting the Java Platform, most notably the Java programming language.

Mnemonic Opcode
(in hexadecimal)
Opcode (in binary) Other bytes Stack
[before]→[after]
Description
aaload 32 0011 0010 arrayref, index → value load onto the stack a reference from an array
aastore 53 0101 0011 arrayref, index, value → store into a reference in an array
aconst_null 01 0000 0001 → null push a null reference onto the stack
aload 19 0001 1001 1: index → objectref load a reference onto the stack from a local variable #index
aload_0 2a 0010 1010 → objectref load a reference onto the stack from local variable 0
aload_1 2b 0010 1011 → objectref load a reference onto the stack from local variable 1
aload_2 2c 0010 1100 → objectref load a reference onto the stack from local variable 2
aload_3 2d 0010 1101 → objectref load a reference onto the stack from local variable 3
anewarray bd 1011 1101 2: indexbyte1, indexbyte2 count → arrayref create a new array of references of length count and component type identified by the class reference index (indexbyte1 << 8 + indexbyte2) in the constant pool
areturn b0 1011 0000 objectref → [empty] return a reference from a method
arraylength be 1011 1110 arrayref → length get the length of an array
astore 3a 0011 1010 1: index objectref → store a reference into a local variable #index
astore_0 4b 0100 1011 objectref → store a reference into local variable 0
astore_1 4c 0100 1100 objectref → store a reference into local variable 1
astore_2 4d 0100 1101 objectref → store a reference into local variable 2
astore_3 4e 0100 1110 objectref → store a reference into local variable 3
athrow bf 1011 1111 objectref → [empty], objectref throws an error or exception (notice that the rest of the stack is cleared, leaving only a reference to the Throwable)
baload 33 0011 0011 arrayref, index → value load a byte or Boolean value from an array
bastore 54 0101 0100 arrayref, index, value → store a byte or Boolean value into an array
bipush 10 0001 0000 1: byte → value push a byte onto the stack as an integer value
breakpoint ca 1100 1010 reserved for breakpoints in Java debuggers; should not appear in any class file
caload 34 0011 0100 arrayref, index → value load a char from an array
castore 55 0101 0101 arrayref, index, value → store a char into an array
checkcast c0 1100 0000 2: indexbyte1, indexbyte2 objectref → objectref checks whether an objectref is of a certain type, the class reference of which is in the constant pool at index (indexbyte1 << 8 + indexbyte2)
d2f 90 1001 0000 value → result convert a double to a float
d2i 8e 1000 1110 value → result convert a double to an int
d2l 8f 1000 1111 value → result convert a double to a long
dadd 63 0110 0011 value1, value2 → result add two doubles
daload 31 0011 0001 arrayref, index → value load a double from an array
dastore 52 0101 0010 arrayref, index, value → store a double into an array
dcmpg 98 1001 1000 value1, value2 → result compare two doubles
dcmpl 97 1001 0111 value1, value2 → result compare two doubles
dconst_0 0e 0000 1110 → 0.0 push the constant 0.0 onto the stack
dconst_1 0f 0000 1111 → 1.0 push the constant 1.0 onto the stack
ddiv 6f 0110 1111 value1, value2 → result divide two doubles
dload 18 0001 1000 1: index → value load a double value from a local variable #index
dload_0 26 0010 0110 → value load a double from local variable 0
dload_1 27 0010 0111 → value load a double from local variable 1
dload_2 28 0010 1000 → value load a double from local variable 2
dload_3 29 0010 1001 → value load a double from local variable 3
dmul 6b 0110 1011 value1, value2 → result multiply two doubles
dneg 77 0111 0111 value → result negate a double
drem 73 0111 0011 value1, value2 → result get the remainder from a division between two doubles
dreturn af 1010 1111 value → [empty] return a double from a method
dstore 39 0011 1001 1: index value → store a double value into a local variable #index
dstore_0 47 0100 0111 value → store a double into local variable 0
dstore_1 48 0100 1000 value → store a double into local variable 1
dstore_2 49 0100 1001 value → store a double into local variable 2
dstore_3 4a 0100 1010 value → store a double into local variable 3
dsub 67 0110 0111 value1, value2 → result subtract a double from another
dup 59 0101 1001 value → value, value duplicate the value on top of the stack
dup_x1 5a 0101 1010 value2, value1 → value1, value2, value1 insert a copy of the top value into the stack two values from the top. value1 and value2 must not be of the type double or long.
dup_x2 5b 0101 1011 value3, value2, value1 → value1, value3, value2, value1 insert a copy of the top value into the stack two (if value2 is double or long it takes up the entry of value3, too) or three values (if value2 is neither double nor long) from the top
dup2 5c 0101 1100 {value2, value1} → {value2, value1}, {value2, value1} duplicate top two stack words (two values, if value1 is not double nor long; a single value, if value1 is double or long)
dup2_x1 5d 0101 1101 value3, {value2, value1} → {value2, value1}, value3, {value2, value1} duplicate two words and insert beneath third word (see explanation above)
dup2_x2 5e 0101 1110 {value4, value3}, {value2, value1} → {value2, value1}, {value4, value3}, {value2, value1} duplicate two words and insert beneath fourth word
f2d 8d 1000 1101 value → result convert a float to a double
f2i 8b 1000 1011 value → result convert a float to an int
f2l 8c 1000 1100 value → result convert a float to a long
fadd 62 0110 0010 value1, value2 → result add two floats
faload 30 0011 0000 arrayref, index → value load a float from an array
fastore 51 0101 0001 arrayref, index, value → store a float in an array
fcmpg 96 1001 0110 value1, value2 → result compare two floats
fcmpl 95 1001 0101 value1, value2 → result compare two floats
fconst_0 0b 0000 1011 → 0.0f push 0.0f on the stack
fconst_1 0c 0000 1100 → 1.0f push 1.0f on the stack
fconst_2 0d 0000 1101 → 2.0f push 2.0f on the stack
fdiv 6e 0110 1110 value1, value2 → result divide two floats
fload 17 0001 0111 1: index → value load a float value from a local variable #index
fload_0 22 0010 0010 → value load a float value from local variable 0
fload_1 23 0010 0011 → value load a float value from local variable 1
fload_2 24 0010 0100 → value load a float value from local variable 2
fload_3 25 0010 0101 → value load a float value from local variable 3
fmul 6a 0110 1010 value1, value2 → result multiply two floats
fneg 76 0111 0110 value → result negate a float
frem 72 0111 0010 value1, value2 → result get the remainder from a division between two floats
freturn ae 1010 1110 value → [empty] return a float
fstore 38 0011 1000 1: index value → store a float value into a local variable #index
fstore_0 43 0100 0011 value → store a float value into local variable 0
fstore_1 44 0100 0100 value → store a float value into local variable 1
fstore_2 45 0100 0101 value → store a float value into local variable 2
fstore_3 46 0100 0110 value → store a float value into local variable 3
fsub 66 0110 0110 value1, value2 → result subtract two floats
getfield b4 1011 0100 2: index1, index2 objectref → value get a field value of an object objectref, where the field is identified by field reference in the constant pool index (index1 << 8 + index2)
getstatic b2 1011 0010 2: index1, index2 → value get a static field value of a class, where the field is identified by field reference in the constant pool index (index1 << 8 + index2)
goto a7 1010 0111 2: branchbyte1, branchbyte2 [no change] goes to another instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
goto_w c8 1100 1000 4: branchbyte1, branchbyte2, branchbyte3, branchbyte4 [no change] goes to another instruction at branchoffset (signed int constructed from unsigned bytes branchbyte1 << 24 + branchbyte2 << 16 + branchbyte3 << 8 + branchbyte4)
i2b 91 1001 0001 value → result convert an int into a byte
i2c 92 1001 0010 value → result convert an int into a character
i2d 87 1000 0111 value → result convert an int into a double
i2f 86 1000 0110 value → result convert an int into a float
i2l 85 1000 0101 value → result convert an int into a long
i2s 93 1001 0011 value → result convert an int into a short
iadd 60 0110 0000 value1, value2 → result add two ints
iaload 2e 0010 1110 arrayref, index → value load an int from an array
iand 7e 0111 1110 value1, value2 → result perform a bitwise and on two integers
iastore 4f 0100 1111 arrayref, index, value → store an int into an array
iconst_m1 02 0000 0010 → -1 load the int value -1 onto the stack
iconst_0 03 0000 0011 → 0 load the int value 0 onto the stack
iconst_1 04 0000 0100 → 1 load the int value 1 onto the stack
iconst_2 05 0000 0101 → 2 load the int value 2 onto the stack
iconst_3 06 0000 0110 → 3 load the int value 3 onto the stack
iconst_4 07 0000 0111 → 4 load the int value 4 onto the stack
iconst_5 08 0000 1000 → 5 load the int value 5 onto the stack
idiv 6c 0110 1100 value1, value2 → result divide two integers
if_acmpeq a5 1010 0101 2: branchbyte1, branchbyte2 value1, value2 → if references are equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_acmpne a6 1010 0110 2: branchbyte1, branchbyte2 value1, value2 → if references are not equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmpeq 9f 1001 1111 2: branchbyte1, branchbyte2 value1, value2 → if ints are equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmpge a2 1010 0010 2: branchbyte1, branchbyte2 value1, value2 → if value1 is greater than or equal to value2, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmpgt a3 1010 0011 2: branchbyte1, branchbyte2 value1, value2 → if value1 is greater than value2, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmple a4 1010 0100 2: branchbyte1, branchbyte2 value1, value2 → if value1 is less than or equal to value2, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmplt a1 1010 0001 2: branchbyte1, branchbyte2 value1, value2 → if value1 is less than value2, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmpne a0 1010 0000 2: branchbyte1, branchbyte2 value1, value2 → if ints are not equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifeq 99 1001 1001 2: branchbyte1, branchbyte2 value → if value is 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifge 9c 1001 1100 2: branchbyte1, branchbyte2 value → if value is greater than or equal to 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifgt 9d 1001 1101 2: branchbyte1, branchbyte2 value → if value is greater than 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifle 9e 1001 1110 2: branchbyte1, branchbyte2 value → if value is less than or equal to 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
iflt 9b 1001 1011 2: branchbyte1, branchbyte2 value → if value is less than 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifne 9a 1001 1010 2: branchbyte1, branchbyte2 value → if value is not 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifnonnull c7 1100 0111 2: branchbyte1, branchbyte2 value → if value is not null, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifnull c6 1100 0110 2: branchbyte1, branchbyte2 value → if value is null, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
iinc 84 1000 0100 2: index, const [No change] increment local variable #index by signed byte const
iload 15 0001 0101 1: index → value load an int value from a local variable #index
iload_0 1a 0001 1010 → value load an int value from local variable 0
iload_1 1b 0001 1011 → value load an int value from local variable 1
iload_2 1c 0001 1100 → value load an int value from local variable 2
iload_3 1d 0001 1101 → value load an int value from local variable 3
impdep1 fe 1111 1110 reserved for implementation-dependent operations within debuggers; should not appear in any class file
impdep2 ff 1111 1111 reserved for implementation-dependent operations within debuggers; should not appear in any class file
imul 68 0110 1000 value1, value2 → result multiply two integers
ineg 74 0111 0100 value → result negate int
instanceof c1 1100 0001 2: indexbyte1, indexbyte2 objectref → result determines if an object objectref is of a given type, identified by class reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokedynamic ba 1011 1010 4: indexbyte1, indexbyte2, 0, 0 [arg1, [arg2 ...]] → result invokes a dynamic method and puts the result on the stack (might be void); the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokeinterface b9 1011 1001 4: indexbyte1, indexbyte2, count, 0 objectref, [arg1, arg2, ...] → result invokes an interface method on object objectref and puts the result on the stack (might be void); the interface method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokespecial b7 1011 0111 2: indexbyte1, indexbyte2 objectref, [arg1, arg2, ...] → result invoke instance method on object objectref and puts the result on the stack (might be void); the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokestatic b8 1011 1000 2: indexbyte1, indexbyte2 [arg1, arg2, ...] → result invoke a static method and puts the result on the stack (might be void); the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokevirtual b6 1011 0110 2: indexbyte1, indexbyte2 objectref, [arg1, arg2, ...] → result invoke virtual method on object objectref and puts the result on the stack (might be void); the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
ior 80 1000 0000 value1, value2 → result bitwise int or
irem 70 0111 0000 value1, value2 → result logical int remainder
ireturn ac 1010 1100 value → [empty] return an integer from a method
ishl 78 0111 1000 value1, value2 → result int shift left
ishr 7a 0111 1010 value1, value2 → result int arithmetic shift right
istore 36 0011 0110 1: index value → store int value into variable #index
istore_0 3b 0011 1011 value → store int value into variable 0
istore_1 3c 0011 1100 value → store int value into variable 1
istore_2 3d 0011 1101 value → store int value into variable 2
istore_3 3e 0011 1110 value → store int value into variable 3
isub 64 0110 0100 value1, value2 → result int subtract
iushr 7c 0111 1100 value1, value2 → result int logical shift right
ixor 82 1000 0010 value1, value2 → result int xor
jsr a8 1010 1000 2: branchbyte1, branchbyte2 → address jump to subroutine at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2) and place the return address on the stack
jsr_w c9 1100 1001 4: branchbyte1, branchbyte2, branchbyte3, branchbyte4 → address jump to subroutine at branchoffset (signed int constructed from unsigned bytes branchbyte1 << 24 + branchbyte2 << 16 + branchbyte3 << 8 + branchbyte4) and place the return address on the stack
l2d 8a 1000 1010 value → result convert a long to a double
l2f 89 1000 1001 value → result convert a long to a float
l2i 88 1000 1000 value → result convert a long to a int
ladd 61 0110 0001 value1, value2 → result add two longs
laload 2f 0010 1111 arrayref, index → value load a long from an array
land 7f 0111 1111 value1, value2 → result bitwise and of two longs
lastore 50 0101 0000 arrayref, index, value → store a long to an array
lcmp 94 1001 0100 value1, value2 → result compare two longs values
lconst_0 09 0000 1001 → 0L push the long 0 onto the stack
lconst_1 0a 0000 1010 → 1L push the long 1 onto the stack
ldc 12 0001 0010 1: index → value push a constant #index from a constant pool (String, int or float) onto the stack
ldc_w 13 0001 0011 2: indexbyte1, indexbyte2 → value push a constant #index from a constant pool (String, int or float) onto the stack (wide index is constructed as indexbyte1 << 8 + indexbyte2)
ldc2_w 14 0001 0100 2: indexbyte1, indexbyte2 → value push a constant #index from a constant pool (double or long) onto the stack (wide index is constructed as indexbyte1 << 8 + indexbyte2)
ldiv 6d 0110 1101 value1, value2 → result divide two longs
lload 16 0001 0110 1: index → value load a long value from a local variable #index
lload_0 1e 0001 1110 → value load a long value from a local variable 0
lload_1 1f 0001 1111 → value load a long value from a local variable 1
lload_2 20 0010 0000 → value load a long value from a local variable 2
lload_3 21 0010 0001 → value load a long value from a local variable 3
lmul 69 0110 1001 value1, value2 → result multiply two longs
lneg 75 0111 0101 value → result negate a long
lookupswitch ab 1010 1011 4+: <0-3 bytes padding>, defaultbyte1, defaultbyte2, defaultbyte3, defaultbyte4, npairs1, npairs2, npairs3, npairs4, match-offset pairs... key → a target address is looked up from a table using a key and execution continues from the instruction at that address
lor 81 1000 0001 value1, value2 → result bitwise or of two longs
lrem 71 0111 0001 value1, value2 → result remainder of division of two longs
lreturn ad 1010 1101 value → [empty] return a long value
lshl 79 0111 1001 value1, value2 → result bitwise shift left of a long value1 by int value2 positions
lshr 7b 0111 1011 value1, value2 → result bitwise shift right of a long value1 by int value2 positions
lstore 37 0011 0111 1: index value → store a long value in a local variable #index
lstore_0 3f 0011 1111 value → store a long value in a local variable 0
lstore_1 40 0100 0000 value → store a long value in a local variable 1
lstore_2 41 0100 0001 value → store a long value in a local variable 2
lstore_3 42 0100 0010 value → store a long value in a local variable 3
lsub 65 0110 0101 value1, value2 → result subtract two longs
lushr 7d 0111 1101 value1, value2 → result bitwise shift right of a long value1 by int value2 positions, unsigned
lxor 83 1000 0011 value1, value2 → result bitwise exclusive or of two longs
monitorenter c2 1100 0010 objectref → enter monitor for object ("grab the lock" - start of synchronized() section)
monitorexit c3 1100 0011 objectref → exit monitor for object ("release the lock" - end of synchronized() section)
multianewarray c5 1100 0101 3: indexbyte1, indexbyte2, dimensions count1, [count2,...] → arrayref create a new array of dimensions dimensions with elements of type identified by class reference in constant pool index (indexbyte1 << 8 + indexbyte2); the sizes of each dimension is identified by count1, [count2, etc.]
new bb 1011 1011 2: indexbyte1, indexbyte2 → objectref create new object of type identified by class reference in constant pool index (indexbyte1 << 8 + indexbyte2)
newarray bc 1011 1100 1: atype count → arrayref create new array with count elements of primitive type identified by atype
nop 00 0000 0000 [No change] perform no operation
pop 57 0101 0111 value → discard the top value on the stack
pop2 58 0101 1000 {value2, value1} → discard the top two values on the stack (or one value, if it is a double or long)
putfield b5 1011 0101 2: indexbyte1, indexbyte2 objectref, value → set field to value in an object objectref, where the field is identified by a field reference index in constant pool (indexbyte1 << 8 + indexbyte2)
putstatic b3 1011 0011 2: indexbyte1, indexbyte2 value → set static field to value in a class, where the field is identified by a field reference index in constant pool (indexbyte1 << 8 + indexbyte2)
ret a9 1010 1001 1: index [No change] continue execution from address taken from a local variable #index (the asymmetry with jsr is intentional)
return b1 1011 0001 → [empty] return void from method
saload 35 0011 0101 arrayref, index → value load short from array
sastore 56 0101 0110 arrayref, index, value → store short to array
sipush 11 0001 0001 2: byte1, byte2 → value push a short onto the stack
swap 5f 0101 1111 value2, value1 → value1, value2 swaps two top words on the stack (note that value1 and value2 must not be double or long)
tableswitch aa 1010 1010 4+: [0-3 bytes padding], defaultbyte1, defaultbyte2, defaultbyte3, defaultbyte4, lowbyte1, lowbyte2, lowbyte3, lowbyte4, highbyte1, highbyte2, highbyte3, highbyte4, jump offsets... index → continue execution from an address in the table at offset index
wide c4 1100 0100 3/5: opcode, indexbyte1, indexbyte2
or
iinc, indexbyte1, indexbyte2, countbyte1, countbyte2
[same as for corresponding instructions] execute opcode, where opcode is either iload, fload, aload, lload, dload, istore, fstore, astore, lstore, dstore, or ret, but assume the index is 16 bit; or execute iinc, where the index is 16 bits and the constant to increment by is a signed 16 bit short
(no name) cb-fd these values are currently unassigned for opcodes and are reserved for future use

See also[edit]

External links[edit]