java8

stream:

集合分組：

Map<String, List<Student>> collect = list.stream().collect(Collectors.groupingBy(Student::getSex));

集合取出某一屬性方法：

List<String> tableNames=list.stream().map(User::getMessage).collect(Collectors.toList());

集合過濾filter：

//過濾出符合條件的數據
List<Apple> filterList = appleList.stream().filter(a -> a.getName().equals("香蕉")).collect(Collectors.toList());

求和：

BigDecimal totalMoney = appleList.stream().map(Apple::getMoney).reduce(BigDecimal.ZERO, BigDecimal::add);

Map轉List：

 

//郵箱集合
List<String> emails = bossCandyGrantBO.getMatchEmail().entrySet()
        .stream().map(entry->entry.getKey()).collect(Collectors.toList());
//設置匹配郵箱入參
MatchUserNoRequest matchEmailUserNoRequest = new MatchUserNoRequest(emails,MatchUserNoRequest.matchEmail);
//批量查詢匹配的郵箱
List<MatchUserNoBO> emailUserNos = memberQueryService.queryMatchEnableUserNo(matchEmailUserNoRequest);
//循環遍歷存入Map
bossCandyGrantBO.getMatchEmail().forEach((k,v)->{
    emailUserNos.stream()
            .filter(o->o.getEmail().equals(k))
            .findFirst().ifPresent(o->userAmountBOList.add(new MatchUserAmountBO(o.getUserNo(),new BigDecimal(v))));
});