Remove Linked List Elements

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

public class Solution {
    public boolean isHappy(int n) {
        HashSet<Integer> hashSet = new HashSet<>();
        while (n != 1) {
        	if (!hashSet.add(n)) {
        		return false;
        	}
        	char[] charArray = String.valueOf(n).toCharArray();
        	int sum = 0;
        	for (char c : charArray) {
        		sum += Math.pow(Integer.valueOf(c + ""), 2);
			}
        	n = sum;
        }
        return true;
    }
}