title: Counting unique characters in a String given by the user
body: <p>I have to write a program that counts the uniques characters in a String given by the user. For example "abc" returns 3 and "aabbccd" returns 4. I am not allow to use  advanced Java classes like Map, Set, etc. I can only use arrays, Strings, for loops, while loops, if statements. I am trying to use a nested loop but am getting confused about how to write the algorithm for the second for loop.</p>
  
  <pre><code>public static int countUniqueCharacters(String input){
  
  String orgInput = input.toLowerCase();
          int count = 0;
          int stringLength = input.length();
          for( int i = 0; i&lt;stringLength; i++){
              for(int j = 2; j &gt; j-i-1; j--){
                  char temp = orgInput.charAt(i);
                  if (temp == orgInput.charAt(j)){
                      count++;
  </code></pre>