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Java bytecode instruction listings
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This is a list of the instructions that make up the Java bytecode
Java bytecode
Java bytecode is the form of instructions that the Java virtual machine executes. Each bytecode opcode is one byte in length, although some require parameters, resulting in some multi-byte instructions. Not all of the possible 256 opcodes are used. 51 are reserved for future use...

, an abstract machine language that is ultimately executed by the Java virtual machine
Java Virtual Machine
A Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...

. The Java bytecode is generated by language compilers targeting the Java Platform, most notably the Java programming language.
Mnemonic Opcode
(in hex)		 Other bytes Stack
[before]→[after]		 Description
aaload 32 arrayref, index → value load onto the stack a reference from an array
aastore 53 arrayref, index, value → store into a reference in an array
aconst_null 01 → null push a null reference onto the stack
aload 19 1: index → objectref load a reference onto the stack from a local variable #index
aload_0 2a → objectref load a reference onto the stack from local variable 0
aload_1 2b → objectref load a reference onto the stack from local variable 1
aload_2 2c → objectref load a reference onto the stack from local variable 2
aload_3 2d → objectref load a reference onto the stack from local variable 3
anewarray bd 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 objectref → [empty] return a reference from a method
arraylength be arrayref → length get the length of an array
astore 3a 1: index objectref → store a reference into a local variable #index
astore_0 4b objectref → store a reference into local variable 0
astore_1 4c objectref → store a reference into local variable 1
astore_2 4d objectref → store a reference into local variable 2
astore_3 4e objectref → store a reference into local variable 3
athrow bf 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 arrayref, index → value load a byte or Boolean value from an array
bastore 54 arrayref, index, value → store a byte or Boolean value into an array
bipush 10 1: byte → value push a byte onto the stack as an integer value
caload 34 arrayref, index → value load a char from an array
castore 55 arrayref, index, value → store a char into an array
checkcast c0 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 value → result convert a double to a float
d2i 8e value → result convert a double to an int
d2l 8f value → result convert a double to a long
dadd 63 value1, value2 → result add two doubles
daload 31 arrayref, index → value load a double from an array
dastore 52 arrayref, index, value → store a double into an array
dcmpg 98 value1, value2 → result compare two doubles
dcmpl 97 value1, value2 → result compare two doubles
dconst_0 0e → 0.0 push the constant 0.0 onto the stack
dconst_1 0f → 1.0 push the constant 1.0 onto the stack
ddiv 6f value1, value2 → result divide two doubles
dload 18 1: index → value load a double value from a local variable #index
dload_0 26 → value load a double from local variable 0
dload_1 27 → value load a double from local variable 1
dload_2 28 → value load a double from local variable 2
dload_3 29 → value load a double from local variable 3
dmul 6b value1, value2 → result multiply two doubles
dneg 77 value → result negate a double
drem 73 value1, value2 → result get the remainder from a division between two doubles
dreturn af value → [empty] return a double from a method
dstore 39 1: index value → store a double value into a local variable #index
dstore_0 47 value → store a double into local variable 0
dstore_1 48 value → store a double into local variable 1
dstore_2 49 value → store a double into local variable 2
dstore_3 4a value → store a double into local variable 3
dsub 67 value1, value2 → result subtract a double from another
dup 59 value → value, value duplicate the value on top of the stack
dup_x1 5a value2, value1 → value1, value2, value1 insert a copy of the top value into the stack two values from the top
dup_x2 5b 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 {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 value3, {value2, value1} → {value2, value1}, value3, {value2, value1} duplicate two words and insert beneath third word (see explanation above)
dup2_x2 5e {value4, value3}, {value2, value1} → {value2, value1}, {value4, value3}, {value2, value1} duplicate two words and insert beneath fourth word
f2d 8d value → result convert a float to a double
f2i 8b value → result convert a float to an int
f2l 8c value → result convert a float to a long
fadd 62 value1, value2 → result add two floats
faload 30 arrayref, index → value load a float from an array
fastore 51 arrayref, index, value → store a float in an array
fcmpg 96 value1, value2 → result compare two floats
fcmpl 95 value1, value2 → result compare two floats
fconst_0 0b → 0.0f push 0.0f on the stack
fconst_1 0c → 1.0f push 1.0f on the stack
fconst_2 0d → 2.0f push 2.0f on the stack
fdiv 6e value1, value2 → result divide two floats
fload 17 1: index → value load a float value from a local variable #index
fload_0 22 → value load a float value from local variable 0
fload_1 23 → value load a float value from local variable 1
fload_2 24 → value load a float value from local variable 2
fload_3 25 → value load a float value from local variable 3
fmul 6a value1, value2 → result multiply two floats
fneg 76 value → result negate a float
frem 72 value1, value2 → result get the remainder from a division between two floats
freturn ae value → [empty] return a float
fstore 38 1: index value → store a float value into a local variable #index
fstore_0 43 value → store a float value into local variable 0
fstore_1 44 value → store a float value into local variable 1
fstore_2 45 value → store a float value into local variable 2
fstore_3 46 value → store a float value into local variable 3
fsub 66 value1, value2 → result subtract two floats
getfield b4 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 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 2: branchbyte1, branchbyte2 [no change] goes to another instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
goto_w c8 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 value → result convert an int into a byte
i2c 92 value → result convert an int into a character
i2d 87 value → result convert an int into a double
i2f 86 value → result convert an int into a float
i2l 85 value → result convert an int into a long
i2s 93 value → result convert an int into a short
iadd 60 value1, value2 → result add two ints
iaload 2e arrayref, index → value load an int from an array
iand 7e value1, value2 → result perform a bitwise and on two integers
iastore 4f arrayref, index, value → store an int into an array
iconst_m1 02 → -1 load the int value -1 onto the stack
iconst_0 03 → 0 load the int value 0 onto the stack
iconst_1 04 → 1 load the int value 1 onto the stack
iconst_2 05 → 2 load the int value 2 onto the stack
iconst_3 06 → 3 load the int value 3 onto the stack
iconst_4 07 → 4 load the int value 4 onto the stack
iconst_5 08 → 5 load the int value 5 onto the stack
idiv 6c value1, value2 → result divide two integers
if_acmpeq a5 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 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 2: branchbyte1, branchbyte2 value1, value2 → if ints are equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmpne a0 2: branchbyte1, branchbyte2 value1, value2 → if ints are not equal, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
if_icmplt a1 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_icmpge a2 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 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 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)
ifeq 99 2: branchbyte1, branchbyte2 value → if value is 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifne 9a 2: branchbyte1, branchbyte2 value → if value is not 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
iflt 9b 2: branchbyte1, branchbyte2 value → if value is less than 0, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
ifge 9c 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 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 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)
ifnonnull c7 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 2: branchbyte1, branchbyte2 value → if value is null, branch to instruction at branchoffset (signed short constructed from unsigned bytes branchbyte1 << 8 + branchbyte2)
iinc 84 2: index, const [No change] increment local variable #index by signed byte const
iload 15 1: index → value load an int value from a local variable #index
iload_0 1a → value load an int value from local variable 0
iload_1 1b → value load an int value from local variable 1
iload_2 1c → value load an int value from local variable 2
iload_3 1d → value load an int value from local variable 3
imul 68 value1, value2 → result multiply two integers
ineg 74 value → result negate int
instanceof c1 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 4: indexbyte1, indexbyte2, 0, 0 [arg1, [arg2 ...]] → invokes a dynamic method identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokeinterface b9 4: indexbyte1, indexbyte2, count, 0 objectref, [arg1, arg2, ...] → invokes an interface method on object objectref, where the interface method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokespecial b7 2: indexbyte1, indexbyte2 objectref, [arg1, arg2, ...] → invoke instance method on object objectref, where the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokestatic b8 2: indexbyte1, indexbyte2 [arg1, arg2, ...] → invoke a static method, where the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
invokevirtual b6 2: indexbyte1, indexbyte2 objectref, [arg1, arg2, ...] → invoke virtual method on object objectref, where the method is identified by method reference index in constant pool (indexbyte1 << 8 + indexbyte2)
ior 80 value1, value2 → result bitwise int or
irem 70 value1, value2 → result logical int remainder
ireturn ac value → [empty] return an integer from a method
ishl 78 value1, value2 → result int shift left
ishr 7a value1, value2 → result int arithmetic shift right
istore 36 1: index value → store int value into variable #index
istore_0 3b value → store int value into variable 0
istore_1 3c value → store int value into variable 1
istore_2 3d value → store int value into variable 2
istore_3 3e value → store int value into variable 3
isub 64 value1, value2 → result int subtract
iushr 7c value1, value2 → result int logical shift right
ixor 82 value1, value2 → result int xor
jsr a8 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 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 value → result convert a long to a double
l2f 89 value → result convert a long to a float
l2i 88 value → result convert a long to a int
ladd 61 value1, value2 → result add two longs
laload 2f arrayref, index → value load a long from an array
land 7f value1, value2 → result bitwise and of two longs
lastore 50 arrayref, index, value → store a long to an array
lcmp 94 value1, value2 → result compare two longs values
lconst_0 09 → 0L push the long 0 onto the stack
lconst_1 0a → 1L push the long 1 onto the stack
ldc 12 1: index → value push a constant #index from a constant pool (String, int or float) onto the stack
ldc_w 13 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 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 value1, value2 → result divide two longs
lload 16 1: index → value load a long value from a local variable #index
lload_0 1e → value load a long value from a local variable 0
lload_1 1f → value load a long value from a local variable 1
lload_2 20 → value load a long value from a local variable 2
lload_3 21 → value load a long value from a local variable 3
lmul 69 value1, value2 → result multiply two longs
lneg 75 value → result negate a long
lookupswitch ab 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 value1, value2 → result bitwise or of two longs
lrem 71 value1, value2 → result remainder of division of two longs
lreturn ad value → [empty] return a long value
lshl 79 value1, value2 → result bitwise shift left of a long value1 by value2 positions
lshr 7b value1, value2 → result bitwise shift right of a long value1 by value2 positions
lstore 37 1: index value → store a long value in a local variable #index
lstore_0 3f value → store a long value in a local variable 0
lstore_1 40 value → store a long value in a local variable 1
lstore_2 41 value → store a long value in a local variable 2
lstore_3 42 value → store a long value in a local variable 3
lsub 65 value1, value2 → result subtract two longs
lushr 7d value1, value2 → result bitwise shift right of a long value1 by value2 positions, unsigned
lxor 83 value1, value2 → result bitwise exclusive or of two longs
monitorenter c2 objectref → enter monitor for object ("grab the lock" - start of synchronized section)
monitorexit c3 objectref → exit monitor for object ("release the lock" - end of synchronized section)
multianewarray c5 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 2: indexbyte1, indexbyte2 → objectref create new object of type identified by class reference in constant pool index (indexbyte1 << 8 + indexbyte2)
newarray bc 1: atype count → arrayref create new array with count elements of primitive type identified by atype
nop 00 [No change] perform no operation
pop 57 value → discard the top value on the stack
pop2 58 {value2, value1} → discard the top two values on the stack (or one value, if it is a double or long)
putfield b5 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 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 1: index [No change] continue execution from address taken from a local variable #index (the asymmetry with jsr is intentional)
return b1 → [empty] return void from method
saload 35 arrayref, index → value load short from array
sastore 56 arrayref, index, value → store short to array
sipush 11 2: byte1, byte2 → value push a short onto the stack
swap 5f value2, value1 → value1, value2 swaps two top words on the stack (note that value1 and value2 must not be double or long)
tableswitch aa 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 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
breakpoint ca reserved for breakpoints in Java debuggers; should not appear in any class file
impdep1 fe reserved for implementation-dependent operations within debuggers; should not appear in any class file
impdep2 ff reserved for implementation-dependent operations within debuggers; should not appear in any class file
(no name) cb-fd these values are currently unassigned for opcodes and are reserved for future use

See also

  • Java bytecode
    Java bytecode
    Java bytecode is the form of instructions that the Java virtual machine executes. Each bytecode opcode is one byte in length, although some require parameters, resulting in some multi-byte instructions. Not all of the possible 256 opcodes are used. 51 are reserved for future use...

    , a general description of the java bytecode within the context of the JVM
  • ARM9E
    ARM9E
    ARM9 is an ARM architecture 32-bit RISC CPU family. With this design generation, ARM moved from a von Neumann architecture to a Harvard architecture with separate instruction and data buses , significantly increasing its potential speed...

    , a CPU
    Central processing unit
    The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

     family with direct Java bytecode execution ability
  • Common Intermediate Language
    Common Intermediate Language
    Common Intermediate Language is the lowest-level human-readable programming language defined by the Common Language Infrastructure specification and is used by the .NET Framework and Mono...

     (CIL), a similar bytecode specification that runs on the CLR
    Common Language Runtime
    The Common Language Runtime is the virtual machine component of Microsoft's .NET framework and is responsible for managing the execution of .NET programs. In a process known as just-in-time compilation, the CLR compiles the intermediate language code known as CIL into the machine instructions...

     of the .NET Framework
    .NET Framework
    The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...

    .
  • C to Java Virtual Machine compilers

External links

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