code: private void addChars(String chars) {
          for (int i = 0; i < chars.length(); i++) {
              int c = chars.codePointAt(i) - min;
              if (values[c] != -1 && values[c] != i) {
                  throw new IllegalArgumentException("Duplicate characters in the encoding alphabet");
              }
              values[c] = i;
          }
      }
docs: Adds the values for the given characters to the value lookup table.
  
  @param chars
  the list of characters to process.