Java – Check if input is a positive integer, negative integer, natural number and so on.

If you really have to avoid operators then use Math.signum()

Returns the signum function of the argument; zero if the argument is
zero, 1.0 if the argument is greater than zero, -1.0 if the argument
is less than zero.

EDIT : As per the comments, this works for only double and float values. For integer values you can use the method:

Integer.signum(int i)