Java: Print a unique character in a string

Question

I'm writing a program that will print the unique character in a string (entered through a scanner). I've created a method that tries to accomplish this but I keep getting characters that are not repeats, instead of a character (or characters) that is unique to the string. I want the unique letters only.

Here's my code:

import java.util.Scanner;
public class Sameness{
   public static void main (String[]args){
   Scanner kb = new Scanner (System.in); 
     String word = "";

     System.out.println("Enter a word: ");
     word = kb.nextLine();

     uniqueCharacters(word); 
}

    public static void uniqueCharacters(String test){
      String temp = "";
         for (int i = 0; i < test.length(); i++){
            if (temp.indexOf(test.charAt(i)) == - 1){
               temp = temp + test.charAt(i);
         }
      }

    System.out.println(temp + " ");

   }
}            

And here's sample output with the above code:

Enter a word: 
nreena
nrea 

The expected output would be: ra

Answer 1

Based on your desired output, you have to replace a character that initially has been already added when it has a duplicated later, so:

public static void uniqueCharacters(String test){
    String temp = "";
    for (int i = 0; i < test.length(); i++){
        char current = test.charAt(i);
        if (temp.indexOf(current) < 0){
            temp = temp + current;
        } else {
            temp = temp.replace(String.valueOf(current), "");
        }
    }

    System.out.println(temp + " ");

}

Answer 2

How about applying the KISS principle:

public static void uniqueCharacters(String test) {
    System.out.println(test.chars().distinct().mapToObj(c -> String.valueOf((char)c)).collect(Collectors.joining()));
}