invokestatic : invoke a class (static) method : index : visitMethodInsn()

Description

invokestatic calls a static method (also known as a class method). For example, if you write in Java:

    System.exit(1);

this is compiled into the JVM code:

    iconst_1      ; push 1 onto the stack.
                  ; now call System.exit()
    invokestatic java/lang/System/exit(I)V

Before performing the method invokation, the class and the method identified by <method-spec> are resolved. See Chapter 9 for a description of how methods are resolved.

invokestatic looks at the descriptor given in <method-spec>, and determines how many arguments the method takes (this may be zero). It pops these arguments off the operand stack. Then it searches the list of static methods defined by the class, locating the method methodname with a descriptor descriptor.

Once the method has been located, invokestatic calls the method. First, if the method is marked as synchronized, the monitor associated with the class object for the method's class is entered. Next, a new stack frame structure is established on the call stack. Then the arguments for the method (which were popped off the current method's operand stack) are placed in local variables of the new stack frame structure. arg1 is stored in local variable 0, arg2 is stored in local variable 1 and so on. Finally, execution continues at the first instruction in the bytecode of the new method.

Methods marked as native are handled slightly differently. For native methods, the runtime system locates the platform-specific code for the method, loading it and linking it into the JVM if necessary. Then the native method code is executed with the arguments that were popped from the operand stack. The exact mechanism used to invoke native methods is implementation-specific.

When the method called by invokestatic returns, any single (or double) word return result is placed on the operand stack of the current method. If the invoked method was marked as synchronized, the monitor associated with the class named in <method-spec> is exited. Execution continues at the instruction that follows invokestatic in the bytecode.

Exceptions

StackOverflowError - no more space in callstack for a new stack frame

See also

invokevirtual invokespecial invokeinterface

Stack

Before	After
argN	[result]
...	...
arg3	...
arg2	...
arg1	...

Bytecode

Type	Description
u1	invokestatic opcode = 0xB8 (184)
u2	index