code: public static String nullify(String value, byte delimiter) {
          // check to see if we need to null out passwords
          if (null == value) {
              return null;
          }
  
          String source = value.toLowerCase();
          StringBuilder b = new StringBuilder(value);
          boolean modified = optionallyMaskChars(b, source, delimiter, PASSWORD_PATTERN);
          modified = optionallyMaskChars(b, source, delimiter, CLIENT_SECRET_PATTERN) || modified;
  
          if (modified) {
              return b.toString();
          }
          return value;
      }
docs: Scan the input value for the "password=" and "client_secret=" key markers
  and convert the password value to a series of *s. The delimiter value
  can be used if the search string is a sequence like
  "key=value<delim>key2=value2".
  
  @param value
  @param delimiter
  @return String