code: public static Properties readProps( URL propsUrl, Properties mappings )
          throws IOException
      {
          InputStream stream = propsUrl.openStream();
          return readProperties( stream, mappings, true );
      }
docs: Read a set of properties from a property file specificed by a url.
  
  @param propsUrl the url of the property file to read
  @param mappings Properties that will be available for translations initially.
  
  @return the resolved properties
  
  @throws IOException if an io error occurs
  @see #readProperties(java.io.InputStream,java.util.Properties,boolean)