Of course, if you put this code into your compiler and run it, you have no idea what will happen, since you never give a value to n.
In general, most loops will have a complexity of O(n) where n is the difference between the initial value and the final value of the index. Most for loops start at 0 or 1 and end at some variable value like n, or size, or so on.
Be careful, though, as some loops are tricky. The following loop, for example, is not O(n) but in fact O(log n):
 for (int i = myList.size(); i > 0; i/=2) {

// ...

}