Check if All Characters Have Equal Number of Occurrences

查一个字符串是不是所有出现过的字符的字频都一样

class Solution {
    public boolean areOccurrencesEqual(String s) {
        int[] count = new int[26];
        for(char c : s.toCharArray())
            count[c - 'a']++;
        Integer j = null;
        for(int c : count)
            if(c != 0){
                if(j == null)
                    j = c;
                else
                    if(c != j)
                        return false;
            }
        return true;
    }
}