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iinc

increment integer in local variable

Jasmin Syntax 


    iinc <varnum> <n>
or
    wide
    iinc <varnum> <n>
In the first form, <varnum> is an unsigned integer in the range 0 to 0xFF and <n> is a signed integer in the range -128 to 127. In the second (wide) form, <varnum> is an unsigned integer in the range 0 to 0xFFFF and <n> is a signed integer in the range -32768 to <= 32767.

Stack

Before

After
...
...
Description

iinc increments the int held in the local variable <varnum> by <n>. The iinc instruction takes two parameters: <varnum> is an unsigned integer which indicates which local variable should be used. <n> is the integer amount to increment or decrement the variable by. <varnum> must be a valid local variable number in the current method's frame.

Example 


iinc 1 10       ; increment local variable 1 by 10.
iinc 1 -1       ; decrement local variable 1 by 1.
Bytecode

For local variable numbers in the range 0-255, and values of <n> in the range -128 to 127, use:

Type

Description
u1
iinc opcode = 0x84 (132)
u1
<varnum>
s1
<n>
There is also a wide format for this instruction, which supports access to all local variables from 0 to 65535, and values of <n> between -32768 and 32767:

Type

Description
u1
wide opcode = 0xC4 (196)
u1
iinc opcode = 0x84 (132)
u2
<varnum>
s2
<n>
See Also

wide

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Java Virtual Machine, by Jon Meyer and Troy Downing, O'Reilly Associates