Listcollect = field.stream().filter(DdlNode.Field::isSelect) .map(DdlNode.Field::getAlias) .filter(org.apache.commons.lang3.StringUtils::isNotBlank) .collect(Collectors.toList());

Listcollect = field.stream().filter(DdlNode.Field::isSelect) .map(DdlNode.Field::getAlias) .filter(org.apache.commons.lang3.StringUtils::isNotBlank) .collect(Collectors.toList());