docs: public final static void appendMailto(final StringBuilder out, final String in, final int start, final int end)
      {
          for (int i = start; i < end; i++)
          {
              final char c;
              final int r = rnd();
              switch (c = in.charAt(i))
              {
              case '&':
              case '<':
              case '>':
              case '"':
              case '\'':
              case '@':
                  if (r < 512)
                  {
                      appendDecEntity(out, c);
                  }
                  else
                  {
                      appendHexEntity(out, c);
                  }
                  break;
              default:
                  if (r < 32)
                  {
                      out.append(c);
                  }
                  else if (r < 520)
                  {
                      appendDecEntity(out, c);
                  }
                  else
                  {
                      appendHexEntity(out, c);
                  }
                  break;
              }
          }
      }