返回字符串中第一个只出现过一次的字符（hash）

public class Try {public static void main(String[] args){String s = "aabcceeff";System.out.println(firstOnce(s));}public static int firstOnce(String s){int hash[] = new int[256];int i = 0;while (i < s.length()){     //遍历字符串，保存每个字符出现的次数hash[s.charAt(i) - '0'] ++;i ++;}i = 0;while (i < s.length()){if (hash[s.charAt(i) - '0'] == 1){    //再次遍历字符串，返回出现次数为1的字符在字符串中对应的位置return i;}else {i ++;}}return -1;}}