将流转换为大小数

Question

我想将流转换为BigDecimal对象。我的代码：

@Named
@Dependent
public class NoteSumOrderValidator implements RosterIntegrityConstraintValidator {

    @Inject
    private MessageBundle bundle;

    @Override
    public List<Notification> validate(Roster roster) {

        Map<String, Map<String, Map<String, Map<String, Map<String, List<RosterRow>>>>>> rost = roster.getRows().stream()
                .collect(Collectors.groupingBy(RosterRow::getBeneficiarySurname,
                        Collectors.groupingBy(RosterRow::getBeneficiaryName,
                                Collectors.groupingBy(RosterRow::getBeneficiaryPatronymic,
                                        Collectors.groupingBy(RosterRow::getBeneficiaryIdentificationDocumentSerial,
                                                Collectors.groupingBy(RosterRow::getBeneficiaryIdentificationDocumentNumber)
                                        )))));

        final BigDecimal MAX_ALLOWED = BigDecimal.valueOf(499_999.99);

        rost.entrySet().stream()
                .map(entry -> rost.get(entry.getKey()))
                .map(each -> each.entrySet())
                .flatMap(Collection::stream)
                .map(entry -> entry.getValue())
                .map(each -> each.entrySet())
                .flatMap(Collection::stream)
                .map(entry -> entry.getValue())
                .map(each -> each.entrySet())
                .flatMap(Collection::stream)
                .map(entry -> entry.getValue())
                .map(each -> each.entrySet())
                .flatMap(Collection::stream)
                .map(entry -> entry.getValue())
                .forEach(group -> {

                    BigDecimal totalAmount = group.stream()
                            .filter(row -> row.getComment().contains("сумма"))
                            .map(RosterRow::getAmount)
                            .reduce(BigDecimal.ZERO, BigDecimal::add);

    //                    List<String> objList = new ArrayList();;
    //                    BigDeciaml bd = group.stream().filter(row -> row.getComment())

                    BigDecimal totalAmount1 = group.stream()
                            .filter(row -> row.getComment().contains("сумма"))
                            .map(BigDecimal::new);


                    BigDecimal totalAmount1 = group.stream()
                            .filter(row -> row.getComment().contains("сумма"))
                            .map(BigDecimal::new);

它说这是不相容的。