Return first digit of an integer

Question

How in Java do you return the first digit of an integer.?

i.e.

345

Returns an int of 3.

Answer 1

public static int firstDigit(int n) {
  while (n < -9 || 9 < n) n /= 10;
  return Math.abs(n);
}

Should handle negative numbers pretty well, too. Will return a negative first digit in that case.

Answer 2

public static void firstDigit(int number){      
    while(number != 0){
        if (number < 10){
            System.out.println("The first digit is " + number);
        }
            number = number/10;

        }
    }

When you call it, you can use Maths.abs in order for it to work for negative number:

firstDigit(Math.abs(9584578)); 

This returns 9

Answer 3

Yet another way:

public int firstDigit(int x) {
  if (x == 0) return 0;
  x = Math.abs(x);
  return (int) Math.floor(x / Math.pow(10, Math.floor(Math.log10(x))));
}

Answer 4

I find this one more simpler:

int firstDigit(int num)
{
    if(num/10 == 0)
        return num;
    return firstDigit(num/10);

}

• Input: 123 => Output: 1
• Input: -123 => Output: -1

Answer 5

int firstNumber(int x){
     int firstN = x;
     while(firstN > 9){
          firstN = (firstN - (firstN%10))/10;
     }
     return firstN;   
 }