public void setCommandButtonVisibility(CommandButton btn, boolean visible) {
        if (btn == null) {
            throw new IllegalArgumentException();
        }

        switch (btn) {
            case SWITCH:
                this.buttonComSwitchVisible = visible;
                break;

            case LOCK:
                this.buttonComLockVisible = visible;
                break;

            case LOGOUT:
                this.buttonComLogOutVisible = visible;
                break;

            case PASSWORD:
                this.buttonComPasswordVisible = visible;
                break;

            case TASKMANAGER:
                this.buttonComTaskmanagerVisible = visible;
                break;

            default:
                break;
        }
    }