i < 0 ? n - ((-i - 1) % n + 1) : i % n
Например:
class Mod {
public static int mod(int i, int n) {
return i < 0 ? n - ((-i - 1) % n + 1) : i % n;
}
public static void main(String [] args) {
System.out.println("mod(-201, 100) == " + mod(-201, 100));
System.out.println("mod(-200, 100) == " + mod(-200, 100));
System.out.println("mod(17, 100) == " + mod(17, 100));
System.out.println("mod(100, 100) == " + mod(100, 100));
}
}
И
$ javac Mod.java && java Mod
mod(-201, 100) == 99
mod(-200, 100) == 0
mod(17, 100) == 17
mod(100, 100) == 0
Без петель.