Iterate through each digit in a number

Question

I am trying to create a program that will tell if a number given to it is a "Happy Number" or not. Finding a happy number requires each digit in the number to be squared, and the result of each digit's square to be added together.

In Python, you could use something like this:

SQUARE[d] for d in str(n) 

But I can't find how to iterate through each digit in a number in Java. As you can tell, I am new to it, and can't find an answer in the Java docs.

Answer 1

You can use a modulo 10 operation to get the rightmost number and then divide the number by 10 to get the next number.

long addSquaresOfDigits(int number) {     long result = 0;     int tmp = 0;     while(number > 0) {         tmp = number % 10;         result += tmp * tmp;         number /= 10;     }     return result; } 

You could also put it in a string and turn that into a char array and iterate through it doing something like Math.pow(charArray[i] - '0', 2.0);

Answer 2

Assuming the number is an integer to begin with:

int num = 56; String strNum = "" + num; int strLength = strNum.length(); int sum = 0;  for (int i = 0; i < strLength; ++i) {   int digit = Integer.parseInt(strNum.charAt(i));   sum += (digit * digit); }