lambad表达式过滤去重

List<String> ids = new ArrayList<>();
    List<BudContentBillVo> duplicateList = billList.stream().filter(// 过滤去重
            v -> {
                boolean flag = !ids.contains(v.getInputGroupId());
                ids.add(v.getInputGroupId());
                return flag;
            }
    ).collect(Collectors.toList());