华为oj之查找字符串中第一次只出现一个的字符

package Ray;

import java.util.Scanner;

public class Try {  
   
    public static void main(String[] args) { 
        Scanner sc = new Scanner(System.in); 
        while(sc.hasNext()){
            String str = sc.nextLine();
            char[] cs = str.toCharArray();
            String s = "-1";
            for(int i = 0; i < cs.length; i++){
                if(str.indexOf(cs[i]) == str.lastIndexOf(cs[i])){
                    s = String.valueOf(cs[i]);
                    break;
                }
            }
            System.out.println(s);
        }
    } 
}