java8 stream list 操作

一、 list转map

1. list 转 map

Map countryMap = countryList.stream().collect(Collectors.toMap(BasicCountryDTO::getCountryCode, t -> t));

2. list 转 map

Map productTypeMap = productTypeList.stream().collect(Collectors.toMap(BasicDictDTO::getCode, BasicDictDTO::getName));

3. list 转map >

Map> um = us.stream().collect(Collectors.groupingBy(SysUserDTO::getUserAccount));

二、list 根据某个字段转list

List accountList = auditUserList.stream().map(SysUserDTO::getUserAccount).collect(Collectors.toList());

三、1.根据key sum

Map sumMap = list.stream().collect(Collectors.groupingBy(item -> item.getA() +item.getB(), Collectors.summingInt(ClassA::getQty)));

2.排序

		List sortClass = list.stream().sorted(Comparator.comparing(ClassA::getField)).collect(Collectors.toList());