code: public static String compactRepeatedChars(@NonNull CharSequence sequence) {
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < sequence.length(); i++) {
           char c = sequence.charAt(i);
           if (builder.length() == 0 || builder.charAt(builder.length() - 1) != c) {
              builder.append(c);
           }
        }
        return builder.toString();
     }
docs: <p>Replaces repeated characters with a single instance. e.g. <code>Gooooood</code> would become
  <code>God</code>.</p>
  
  @param sequence The character sequence
  @return The compacted string
  @throws NullPointerException when the sequence is null