code: private boolean differentChars(char c1, char c2) {
          if (65 <= c1 && c1 < 97) {
              c1 +=32;
          }
  
          if (65 <= c2 && c2 < 97) {
              c2 +=32;
          }
          return c1 != c2;
      }
docs: Compares two chars.
  
  @param c1 the first char
  @param c2 the second char
  @return true if first and second chars are different.