code: @Override
      protected void encode() {
  
          if (!content.matches("[0-9A-Z\\. \\-$/+%]+")) {
              throw new OkapiException("Invalid characters in input");
          }
  
          String p = "";
          int l = content.length();
          int charval, counter = 0;
          char thischar;
          char checkDigit;
          for (int i = 0; i < l; i++) {
              thischar = content.charAt(i);
              charval = positionOf(thischar, LOOKUP);
              counter += charval;
              p += CODE39LM[charval];
          }
  
          counter = counter % 43;
          checkDigit = LOOKUP[counter];
          encodeInfo += "Check Digit: " + checkDigit + "\n";
          p += CODE39LM[counter];
  
          readable = content + checkDigit;
          pattern = new String[] { "1311313111" + p + "131131311" };
          row_count = 1;
          row_height = new int[] { -1 };
      }
docs: {@inheritDoc}