java jdk8语法记录

1.过滤出想要的结果 取第一个

Optional stock = vo.stream().filter(v->“100”.equals(page.getProductCode())).findFirst();
if (stock.isPresent()) {
StockWarQueryVo stock4 = stock.get();
stockVo.setProductName(stock4.getProductName());
}

2.过滤出想要的结果集

List vehicleInfos = list.stream().filter(a ->100==a.getSysOrgId()).collect(Collectors.toList());

3.取出ids

List productCodes = vo.stream().map(StockWarQueryVo::getProductCode).collect(Collectors.toList());

4.list转为id为key的map

Map<Long, User> maps = userList.stream().collect(Collectors.toMap(User::getId,Function.identity()));

5.根据属性分组

Map<String, List> detailsMap01 = list.stream()
.collect(Collectors.groupingBy(User::getId));

6.排序

(1)升序

Collections.sort(result, Comparator.comparing(ProVendorCategoryTreeVo::getClassifySort));

(2)降序

Collections.sort(result, Comparator.comparing(ProVendorCategoryTreeVo::getClassifySort).reversed());

(3)先升序再降序

Collections.sort(result, Comparator.comparing(ProVendorCategoryTreeVo::getClassifySort)).thenComparing(ProVendorCategoryTreeVo::getId).reversed();