Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.s = "loveleetcode",
return 2.

public class Solution {public int firstUniqChar(String s) {if (s == null || s.length() == 0) {return -1;}HashMap<Character, Integer> map = new HashMap<Character, Integer>();for (int i = 0; i < s.length(); i++) {Integer in = map.get(s.charAt(i));if (in == null) map.put(s.charAt(i), 1);elsemap.put(s.charAt(i), 2);}for (int i = 0; i < s.length(); i++) {if(map.get(s.charAt(i)) == 2) {continue;} else {if (map.get(s.charAt(i)) == 1) {return i;}}} return -1;}
}