一些常见的Java8 循环实例（筛选、基本函数使用，循环等）

1.java8 list集合按着某个字段分组后转map

Map<Integer, List<SopEntity>> sopIdListMap =
                    sopEntities.stream().collect(Collectors.groupingBy(SopEntity::getId));

2.Java8 list集合去重（根据ID）

List<User> list = userList.stream()
						.collect(Collectors.collectingAndThen(Collectors.toCollection(() ->                 
     new TreeSet<>(Comparator.comparing(User::getUserId))), ArrayList::new));

3.Java8 list集合去除null值

List<user> result = list.stream().filter(item -> 
                          item.getUserId!=null).collect(Collectors.toList());

4.Java8 普通集合对象转map

Map<Long, VipEntity> vipMap = vipList
				.stream().collect(Collectors
					.toMap(VipEntity::getUserId, v -> v, (v1, v2) -> v1));

5.Java8 集合数据(可根据时间或年龄等)排序 升序或降序

   dtoList.sort((m1, m2) -> m2.getPunchTime().compareTo(m1.getPunchTime()));
   list.stream().sorted(Comparator.comparing(ServicePlan::getCreateTime).reversed()) 

6.Java8 是否所有数据都满足某个条件

Boolean anyOldThan50 = pigs.stream().anyMatch(a -> a.getAge() > 50);//是否有1条age>50
Boolean allLittleThan50 = pigs.stream().allMatch(a -> a.getAge() < 50);//是否所有数据都满足age<50
Boolean noneLittleThan50 = pigs.stream().noneMatch(a -> a.getAge() < 50);//是否所有数据都不满足age<50

7.Java8 自带求和等函数

int sumAge = pigs.stream().mapToInt(Pig::getAge).sum();
int maxAge = pigs.stream().mapToInt(Pig::getAge).max().getAsInt();
int minAge = pigs.stream().mapToInt(Pig::getAge).min().getAsInt();
double avgAge = pigs.stream().mapToInt(Pig::getAge).average().getAsDouble();

8.Java8 list数据筛选、模糊

ist<MerchantManagementVo> result = resultList.stream()
                        .filter(item -> item.getManagerName()!=null &&
                                        item.getManagerName().contains((CharSequence) 
 map.get("managerName"))).collect(Collectors.toList());

9.java8 两个list集合合并并去重（俩list必须一致）

List<String> list = Stream.of(list1, list2)
                      .flatMap(Collection::stream).distinct().collect(Collectors.toList());

10.java8 筛选出两个不同集合不同字段 的相同数据

    userList = list.stream().filter(item -> !(voList.stream().map(e -> e.getName())
                        .collect(Collectors.toList()).contains(item.getName())))
                    .collect(Collectors.toList());