Retrieving the first digit of a number

Question

Hi, I am just learning Java and am trying to get my program to retrieve the first digit of a number - for example 543 should return 5, etc. I thought to convert to a string, but I am not sure how I can convert it back? Thanks for any help.

int number = 534;
String numberString = Integer.toString(number);
char firstLetterChar = numberString.charAt(0);
int firstDigit = ????

Answer 1

    int number = 534;
    int firstDigit = Integer.parseInt(Integer.toString(number).substring(0, 1));

Answer 2

Integer.parseInt will take a string and return a int.

Answer 3

int firstDigit = Integer.parseInt(Character.toString(firstLetterChar));

Answer 4

int number = 534;
String numberString = "" + number;
char firstLetterchar = numberString.charAt(0);
int firstDigit = Integer.parseInt("" + firstLetterChar);

Answer 5

firstDigit = number/((int)(pow(10,(int)log(number)));

This should get your first digit using math instead of strings.

In your example log(543) = 2.73 which casted to an int is 2. pow(10, 2) = 100 543/100 = 5.43 but since it's an int it gets truncated to 5

Answer 6

Almost certainly more efficient than using Strings:

int firstDigit(int x) {
    while (x > 9) {
        x /= 10;
    }
    return x;
}

(Works only for nonnegative integers.)