查找字符串中第一个不重复的字符的方法。

//The position of the charactor in string 's' equals to the position of that charactor last occurs in the same string,then the charactor just occurs once,and it will be the first //no-repeatable charactor in string 's'.

public static String findFirst(String s) {

        for(int i=0; i<s.length(); i++) {
            String currentChar = String.valueOf(s.charAt(i));
            if(s.indexOf(currentChar) == s.lastIndexOf(currentChar)) {
                return currentChar;
            }
        }
        return null;

 }