如何使用java流响应子对象

Question

好吧，我一整天都在胡思乱想，解决不了这个问题。我正试图在对象列表中找到一个id，该id与java流类似于层次结构中的3层。我知道如何使用for循环来实现它，但是我需要使用流来实现它。json响应是

​

"NumberOfOwners": 1,
    "CurrentPage": 1,
    "TotalItems": 1,
    "TotalPages": 1,
    "PageSize": 1,
    "PageItems": [
        {
            "Id": 1560,
            "Title": "PlsWrk",
            "IsSubmitted": true,
            "Owner": {
                "Branch": null,
                "Position": null,
                "Id": null,
                "FirstName": null,
                "LastName": null,
                "ParentName": null,
                "Gender": null,
                "Image": null,
                "LoginStatusId": 0,
                "EmployeeStatus": 0,
                "CompanyName": null,
                "IsSubcontractor": false
            },
            "KeyResults": [
                {
                    "Id": 5032,
                    "Title": "asdf1",
                    "OverallStatus": 2,
                    "MonthKeyResults": [
                        {
                            "Id": 12484,
                            "Month": 9,
                            "Status": 3,
                            "Progress": "REaplace1"
                        },
                        {
                            "Id": 12483,
                            "Month": 8,
                            "Status": 3,
                            "Progress": "sadf4"
                        },
                        {
                            "Id": 12482,
                            "Month": 7,
                            "Status": 1,
                            "Progress": "On Track1"
                        }
                    ]
                },
                {
                    "Id": 5033,
                    "Title": "asdf2",
                    "OverallStatus": 1,
                    "MonthKeyResults": [
                        {
                            "Id": 12485,
                            "Month": 7,
                            "Status": 2,
                            "Progress": "Recovery2"
                        },
                        {
                            "Id": 12487,
                            "Month": 9,
                            "Status": 2,
                            "Progress": "asdfreas"
                        },
                        {
                            "Id": 12486,
                            "Month": 8,
                            "Status": 1,
                            "Progress": "asdf5"
                        }
                    ]
                },
                {
                    "Id": 5034,
                    "Title": "asdf3",
                    "OverallStatus": 2,
                    "MonthKeyResults": [
                        {
                            "Id": 12490,
                            "Month": 9,
                            "Status": 1,
                            "Progress": "asdafa"
                        },
                        {
                            "Id": 12489,
                            "Month": 8,
                            "Status": 2,
                            "Progress": "asdf6"
                        },
                        {
                            "Id": 12488,
                            "Month": 7,
                            "Status": 3,
                            "Progress": "Replace3"
                        }
                    ]
                }
            ]
        }
    ]

​

确切地说，我希望流返回具有特定id Atm的MonthyKeyResult对象。

​

public static MonthKeyResults getOkrMonthlyProgressById(PageItems okr, Integer monthlyProgressId){

        //here i get KeyResults object list
        List<KeyResults> keyResult = okr.getKeyResults().stream().collect(Collectors.toList());
            
            //and now I am trying to get all MonthKeyResults 
            //objects but I not doing it right
            List<MonthKeyResults> monthKeyResults = keyResult.stream().
                       filter(monthKeyResult -> monthKeyResult.
                                  getMonthKeyResults().
                                  stream().collect(Collectors.toList()));
            
            //and then I am thinking of going trough the monthKeyResults 
            //list with stream and finding Id I need and returning that 
            //whole object with something like this
    MonthKeyResults mKeyResults = monthKeyResults.stream().filter(id -> id.getId().
                    equals(monthlyProgressId)).findAny().orElse(null);
    return mKeyResult
}

我还有一个问题--我已经把最后一个对象分开了--就像你在3条流中看到的那样，你能一次得到它吗?还是你需要像这样把这些对象分开，然后把它们分开处理？

​

Answer 1

也许你在找的东西是：

return okr.getKeyResults().stream()
        .flatMap(keyResult -> keyResult.getMonthKeyResults().stream())
        .filter(monthKeyResult -> monthKeyResult.getId().equals(monthlyProgressId))
        .findAny()
        .orElse(null);

编辑:修正错误。