387. First Unique Character in a String

class Solution {
    public int firstUniqChar(String s) {
          int indx = -1;
        Map<Character, Integer> mp = new HashMap<>();
        for (int i = 0; i < s.length(); i++) {
            mp.put(s.charAt(i), mp.getOrDefault(s.charAt(i), 0)+1);
        }
        for (int i = 0; i < s.length(); i++) 
            if(mp.get(s.charAt(i)) == 1) return i;
        
        return -1;
    }
}