找出字符串中第一个只出现一次的字符

import java.util.Scanner;

public class GetOneChar {

public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String str = scan.nextLine();
int count = 0;
for (int i = 0; i < str.length(); i++) {
int a = str.indexOf(str.charAt(i));
int b = str.lastIndexOf(str.charAt(i));
if(a-b==0){
System.out.println(str.charAt(i));
return;
}
count++;
}
if(count==str.length())
System.out.println(".");
}

}