Try this :
Working Example
public class Main {
public static void main(String[] args) {
long num = -23;
int digits = 0;
if (num < 0)
num *= (-1);
if (num < 10 && num >= 0)
digits = 1;
else {
while(num > 0) {
num /= 10;
digits++;
}
}
System.out.println("Digits: " +digits);
}
}