@NonNull
    public static Set<String> keySet(@Nullable Bundle bundle) {
        if (bundle == null) {
            return Collections.emptySet();
        }
        return bundle.keySet();
    }
@ NonNull public static Set < String > keySet ( @ Nullable Bundle bundle ) { if ( bundle == null ) { return Collections . emptySet ( ) ; } return bundle . keySet ( ) ; }
Returns a set of keys in the bundle.
@param bundle a bundle.
@return a set of keys in the bundle. Empty set if bundle is null.
@see android.os.Bundle#keySet()