code: private char[] getConstantChars() {
          Set<Character> chars = new TreeSet<Character>();
          chars.add('\n');
          chars.add('\r');
          for (PatternConstant constant : constantSet) {
              char c = constant.getValue().charAt(0);
              if (constant.isIgnoreCase()) {
                  chars.add(Character.toLowerCase(c));
                  chars.add(Character.toUpperCase(c));
              } else {
                  chars.add(c);
              }
          }
  
          char[] cs = new char[chars.size()];
          int j = 0;
          for (Character c : chars) {
              cs[j] = c;
              j++;
          }
          Arrays.sort(cs);
          return cs;
      }
docs: Collect first chars of constants of configuration.
  
  @return array of first chars of constants.