code: public static String decode(String s, String enc, boolean decodeSlash, StringBuilder buffer) {
          return decode(s, enc, decodeSlash, true, buffer);
      }
docs: Decodes a URL. If the decoding fails for any reason then an IllegalArgumentException will be thrown.
  
  @param s           The string to decode
  @param enc         The encoding
  @param decodeSlash If slash characters should be decoded
  @param buffer      The string builder to use as a buffer.
  @return The decoded URL