The Java® Virtual Machine Specification, Java SE 7 Edition, Third Edition

3.6. Receiving Arguments

If n arguments are passed to an instance method, they are received, by convention, in the local variables numbered 1 through n of the frame created for the new method invocation. The arguments are received in the order they were passed. For example:

int addTwo(int i, int j) {     return i + j; }

compiles to:

Method int addTwo(int,int) 0   iload_1         // Push value of local variable 1 (i) 1   iload_2         // Push value of local variable 2 (j) 2   iadd            // Add; leave int result on operand stack 3   ireturn         // Return int result

By convention, an instance method is passed a reference to its instance in local variable 0. In the Java programming language the instance is accessible via the this keyword. ...