String a = (String) s.getChildItem(Signal.PREDICATE);
String a = (String) s.getChild(Signal.PREDICATE);
    public void control(Signal s) throws Exception {        if (s != null) {            String a = (String) s.getChildItem(Signal.PREDICATE);            if (a != null) {                if (a.isEqualTo(Controller.SHOW_SYSTEM_USER_INTERFACE_ACTION)) {                    log(Controller.INFO_LOG_LEVEL, "Show system user interface.");                    showSystemUserInterface(s);                    } else if (a.isEqualTo(Controller.HIDE_SYSTEM_USER_INTERFACE_ACTION)) {                        log(Controller.INFO_LOG_LEVEL, "Hide system user interface.");                    hideSystemUserInterface(s);                } else if (a.isEqualTo(Controller.SHOW_SYSTEM_INFORMATION_USER_INTERFACE_ACTION)) {                    log(Controller.INFO_LOG_LEVEL, "Show system information user interface.");                    showSystemInformationUserInterface(s);                    } else if (a.isEqualTo(Controller.HIDE_SYSTEM_INFORMATION_USER_INTERFACE_ACTION)) {                    log(Controller.INFO_LOG_LEVEL, "Hide system information user interface.");                    hideSystemInformationUserInterface(s);                    } else if (a.isEqualTo(Controller.MOUSE_CLICKED_ACTION)) {                    log(Controller.INFO_LOG_LEVEL, "Mouse clicked.");                    mouseClicked(s);                }            } else {                throw new Exception("Could not process action. The action is null.");            }        } else {            throw new Exception("Could not control signal. The signal is null.");        }    }