When arguments are passed to a method, they are copies of the original value. And these copies are local to the method scope.
In this case, there is an int i defined in the class, another int i defined in the main method, and a third int i that's local to the change_i method. So when the value of i is changed within the change_i method, it's only that local value that changes. The int i within main is still 1, and the int i defined at the class level is still 0.
Compile and run the code below, which I've modified to output each of these different variables...
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org