code: public String decode(String text) {
      if (text == null) { return null; }
      if ((!text.startsWith(Prefix)) || (!text.endsWith(Postfix)))
        throw new IllegalArgumentException("RFC 1522 violation: malformed encoded content");
      int terminator = text.length() - 2;
      int from = 2;
      int to = text.indexOf(Sep, from);
      if (to == terminator) throw new IllegalArgumentException("RFC 1522 violation: charset token not found");
      String charset = text.substring(from, to);
      if (charset.equals("")) throw new IllegalArgumentException("RFC 1522 violation: charset not specified");
      from = to + 1;
      to = text.indexOf(Sep, from);
      if (to == terminator) throw new IllegalArgumentException("RFC 1522 violation: encoding token not found");
      String encoding = text.substring(from, to);
      if (!getEncoding().equalsIgnoreCase(encoding))
        throw new IllegalArgumentException("This codec cannot decode " + encoding + " encoded content");
      from = to + 1;
      to = text.indexOf(Sep, from);
      return new String(Base64.decode(text.substring(from, to).toCharArray()), Charset.forName(charset));
    }
docs: Decodes a Base64 string into its original form. Escaped characters are converted back to their
  original
  representation.
  
  @param value Base64 string to convert into its original form
  @return original string