Question

我有以下类型的地图：

[
    {
        "RequestId": 453,
        "RequestGuid": "a81b5878-6214-44b4-8888-aab46ce48adf",
        "ShowRecordingInfo": true,
        "IsOfficeDetailsRequest": false,
        "UserId": 8515,
        "IsSaved": true,
        "Name": "saving test check no link to ODP",
        "DocumentTypeDetails": {
            "PageRec": "AL005",
            "State": "AL",
            "County": "Autauga County",
            "CityTown": null,
            "Zip": null,
            "ShowRecordingInfo": "true",
            "Deed": {
                "Checked": "True",
                "Pages": "1",
                "ConsiderationAmount": "150000"
            },
            "Amend": {
                "Checked": "False",
                "Pages": "1",
                "ConsiderationAmount": "150000"
            },
            "MortgageDeed": {
                "Checked": "False",
                "Pages": null,
                "NewDebtAmount": null
            },
            "MortgageMod": {
                "Checked": "False",
                "Pages": null,
                "NewDebtAmount": null
            },
            "MortgageRefi": {
                "Checked": "False",
                "Pages": null,
                "NewDebtAmount": null,
                "OriginalDebt": null,
                "UnpaidDebt": null
            },
            "Assignment": {
                "Checked": "False",
                "Pages": null,
                "Assignments": null
            },
            "ReleaseSatisfaction": {
                "Checked": "False",
                "Pages": null,
                "ReleasesSatisfactions": null
            },
            "poa":{
                "Checked":"False",
                "Pages":null
            },
            "Questions": {
                "Question": {
                    "Number": "Q4",
                    "Category": "Deed",
                    "Type": "bool",
                    "QuestionText": "Are the deed and mortgage being recorded at the same time?",
                    "Answer": "1"
                }
            }
        },
        "RequestXml": {
            "App": "B",
            "Authentication": {
                "UserID": "",
                "Password": ""
            },
            "TransactionDate": "1/27/2016",
            "TransactionCode": "150",
            "Property": {
                "Page": "AL005",
                "City": null,
                "County": null,
                "State": "AL",
                "EstimatedValue": "150000",
                "MortgageAmount": null,
                "OriginalDebtAmount": null,
                "UnpaidPrincipalBalance": null,
                "OriginalMortgageDate": null,
                "StateQuestions": {
                    "Q1": "0",
                    "Q2": "0",
                    "Q3": "0",
                    "Q4": "1",
                    "Q5": "0",
                    "Q6": "0",
                    "Q7": "0",
                    "Q8": "0",
                    "Q9": "0",
                    "Q10": "0",
                    "Q11": "0",
                    "Q12": "0",
                    "Q13": "0",
                    "Q14": "0",
                    "Q15": "0",
                    "Q16": "0",
                    "Q17": "0",
                    "Q18": "0",
                    "Q19": "0",
                    "Q20": "0",
                    "Q21": "0",
                    "V1": "0",
                    "V2": "0",
                    "V3": "0",
                    "V4": "0"
                }
            },
            "NumberOfPages": {
                "Mortgage": null,
                "Deed": "1"
            },
            "Assignment": {
                "Pages": null,
                "NumberOfAssignments": null
            },
            "Release": {
                "Pages": null,
                "NumberOfReleases": null
            },
            "DataSource": "P"
        },

        }
    }
]

键从1 - n开始。整个Map中的subMap具有以下类型：

private HashMap<Integer, HashMap<String, Object>> entireMap;

整个地图的每个键都包含这个子地图（还有更多）：

HashMap<String, Object> subMap = new HashMap<String, Object>();

所以我最后有这样的事情：

subMap.put("user_name", usid[1]);

现在我想计算整个地图中user_name的最大出现次数，在这种情况下它将是3（bela发生三次）。

我该怎么做？

Answer 1

以下是一个实现示例。

注意：请勿在生产代码中使用此类地图初始化！

    HashMap<Integer, HashMap<String, Object>> entireMap = new HashMap<>();
    entireMap.put(1, new HashMap<String, Object>() {{
        put("user_name", "Arthur");
        put("other_key1", "val");
        put("other_key2", "val");
    }});
    entireMap.put(2, new HashMap<String, Object>() {{
        put("user_name", "Bela");
        put("other_key2", "val");
    }});
    entireMap.put(3, new HashMap<String, Object>() {{
        put("user_name", "Ceasar");
    }});
    entireMap.put(4, new HashMap<String, Object>() {{
        put("user_name", "Ceasar");
    }});
    entireMap.put(5, new HashMap<String, Object>() {{
        put("user_name", "Bela");
    }});
    entireMap.put(6, new HashMap<String, Object>() {{
        put("user_name", "Bela");
    }});

    Map<Object, Long> result = entireMap
            .values()
            .stream()
            .map(map -> map.get("user_name"))
            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

    System.out.println(result);

    Long max = Collections.max(result.values());
    System.out.println(max);

输出：

{Ceasar=2, Arthur=1, Bela=3}
3

Answer 2

如果您不想使用java 8功能，只需通过简单的迭代遍历地图即可。

Map<String, Integer> resultMap = new HashMap<String, Integer>();

for (int key : entireMap.keySet()) {
    String userName = (String) entireMap.get(key).get("user_name");

    if (resultMap.containsKey(userName)) {
        resultMap.put(userName, resultMap.get(userName) + 1);
    } else {
        resultMap.put(userName, 1);
    }
}

System.out.println(resultMap);

输出

{Arthur = 1，Ceasar = 2，Bela = 3}

Answer 3

以下是使用Java 8功能的一种方法，但没有流：

counts

在Entry<String, Long> max = Collections.max( counts.entrySet(), Map.Entry.comparingByValue());地图中，您将拥有每个用户的计数。然后，您可以找到具有最大值的条目：

SomeResponse

Answer 4

在Java 7或更低版本中，您可以使用Guava MultiSet：

List<Object> names = new ArrayList<>();
for (HashMap<String, Object> outerMap : entireMap.values()) {
    names.add(outerMap.get("user_name"));
}

HashMultiset<Object> objects = HashMultiset.create(names);

objects.forEachEntry((name, count) -> System.out.println(name + " -> " + count));

结果：

Ceasar -> 2
Arthur -> 1
Bela -> 3

计算地图中值的出现次数

4 个答案: