question: public static List < UserLayer > extractUserLayers ( StyledLayerDescriptor sld ) { List < UserLayer > userLayerList = new ArrayList < UserLayer > ( ) ; if ( sld != null ) { for ( StyledLayer layer : sld . layers ( ) ) { if ( layer instanceof UserLayer ) { UserLayer userLayer = ( UserLayer ) layer ; userLayerList . add ( userLayer ) ; } } } return userLayerList ; }
target:  Extract user layers from an SLD.