题解 | #第一个只出现一次的字符#

public class Solution {
    public int FirstNotRepeatingChar(String str) {
        if(str == null || str.length() == 0) {
            return -1;
        }
        int[] counts = new int[128];
        char[] arr = str.toCharArray();
        for(char ch : arr) {
            counts[ch]++;
        }
        for(int i = 0; i < arr.length; i++) {
            if(counts[arr[i]] == 1) {
                return i;
            }
        }
        return -1;
    }
}