code: public static final void setStringAttribute(Path path, String attribute, String value, LinkOption... options) throws IOException
      {
          attribute = attribute.startsWith("user:") ? attribute : "user:"+attribute;
          if (value != null)
          {
              Files.setAttribute(path, attribute, value.getBytes(UTF_8), options);
          }
          else
          {
              Files.setAttribute(path, attribute, null, options);
          }
      }
docs: Set user-defined-attribute
  @param path
  @param attribute user:attribute name. user: can be omitted.
  @param value
  @param options
  @throws IOException