JZ34 第一个只出现一次的字符

https://www.nowcoder.com/practice/1c82e8cf713b4bbeb2a5b31cf5b0417c

import java.util.HashMap;

public class Solution {
   HashMap<Character, Integer> map = new HashMap<>();
 
    public int FirstNotRepeatingChar(String str) {
        if (str==null)return -1;
        int length = str.length();
        for(int i = 0;i<length;i++) {
             
            if(map.containsKey(str.charAt(i))){
                int value = map.get(str.charAt(i));
                map.put(str.charAt(i),value+1);
            }else{
                map.put(str.charAt(i),1);
            }
        }
     for(int i = 0;i<length;i++){
         if(map.get(str.charAt(i))==1)
             return i;
        }
        return -1;  
    }
}