Invoke instance method
Bytecode
Type | Description |
u1 | invokevirtual opcode = 0xD6 (214) |
u1 | index |
u1 | nargs |
Stack ..., objectref, [arg1, [arg2 ...]] => ...
Description
The objectref must be of type reference
and must reference a class
instance. The index operand is an unsigned byte, and the nargs operand is an
unsigned byte, which must not be zero. The index is an index into the method table
of the class of the type of objectref. The table entry at that index includes the
method's code and its modifier information.
If the method is synchronized
, the monitor associated
with objectref is acquired.
If the method is not native
, the nargs - 1
words of arguments and objectref are popped from the operand stack. A new stack
frame is created for the method being invoked, and objectref and the words of
arguments are made the values of its first nargs local variables, with objectref
in local variable 0, arg1 in local variable 1, and so on. The new
stack frame is then made current, and the Java Virtual Machine pc
is set to
the opcode of the first instruction of the method to be invoked. Execution continues with
the first instruction of the method.
If the method is native
and the
platform-dependent code that implements it has not yet been loaded and linked into the
Java Virtual Machine, that is done. The nargs - 1 words of arguments and objectref
are popped from the operand stack; the code that implements the method is invoked in an
implementation-dependent manner.
NullPointerException - objectref is null
The opcode of this instruction was originally invokevirtual, with objectref
not referring to an instance of java.lang.Object
and with operands determined
dynamically to represent a method with a method table index of 255 or less. When the
constant pool entry referenced by an invokevirtual instruction is resolved, a
one-byte index for the method it references is generated. That index replaces the first
operand byte of the original invokevirtual instruction. The second operand byte of
the invokevirtual instruction is replaced by nargs, the number of argument
words expected by the method.
An invokevirtual instruction referring to an instance of java.lang.Object
and with operands representing a constant pool index of 255 or less will instead be
converted into an invokevirtualobject_quick instruction. Any invokevirtual
instruction with operands representing a constant pool index greater than 255 will be
converted into an invokevirtual_quick_w instruction.