去重：
List<String> unique = doccodeList.stream().distinct().collect(Collectors.toList());

判空：

List<String> doccodeList = allCuiji.stream().map(CuijiBean::getDoccode).filter(x -> x !=null&&! x.equals("") ).collect(Collectors.toList());

根據屬性過濾：

List<CuijiBean> filterList = allCuiji.stream().filter(a ->
                                       one.equals(a.getDoccode())).collect(Collectors.toList());