Stream常见用法

boolean isFound = userList.stream().anyMatch(user -> Objects.equals(user.getId(), userId));

List<UserDO> resultList = userList.stream()
    .filter(user -> Boolean.TRUE.equals(user.getIsSuper()))
    .collect(Collectors.toList());

double total = accountList.stream().mapToDouble(Account::getBalace).sum();

List<UserVO> userVOList = userDOList.stream().map(this::transUser).collect(Collectors.toList());

Map<Long, List<UserDO>> roleUserMap = userDOList.stream()
    .collect(Collectors.groupingBy(UserDO::getRoleId));

roleTotalMap = accountList.stream()
    .collect(Collectors.groupingBy(Account::getRoleId,Collectors.summingDouble(Account::getBalance)));

int[] array1 = IntStream.rangeClosed(1,N).toArray();
int[] array2 = IntStream.iterate(1, n -> n*2).limit(N).toArray();