classloader.getSystemResourceAsStream returns null

The PROPERTIES_FILE constant should include the package as well as the properties file (e.g. "com/some/library/file.properties".

    final static String PROPS_FILE = "/com/some/library/file.props";
                     //The preceding  "/" is dependendant on wheterh 
                     //you are going to be giving a relative or absolute location
    InputStream is = YourCurrentClass.class.getResourceAsStream(PROPS_FILE);