java如何使用hashmap和arraylist的循环逻辑？

Question

我有以下代码：

public static void main(String args[]) throws JsonProcessingException {

    List<Map<Object, Object>> dataProviderList = new LinkedList<>();

    List<String> X_AxesList = new LinkedList<>();
    List<String> Y_AxesList = new LinkedList<>();
    List<Integer> ValueList = new LinkedList<>();

    X_AxesList.add("Arizona");
    X_AxesList.add("Arkansas");
    X_AxesList.add("Florida");
    X_AxesList.add("Ohio");
    X_AxesList.add("WashingtonDC");

    Y_AxesList.add("2012");
    Y_AxesList.add("2013");
    Y_AxesList.add("2014");
    Y_AxesList.add("2015");

    ValueList.add(20);
    ValueList.add(30);
    ValueList.add(10);
    ValueList.add(40);
    ValueList.add(50);
    ValueList.add(15);
    ValueList.add(35);
    ValueList.add(42);
    ValueList.add(85);
    ValueList.add(19);
    ValueList.add(16);
    ValueList.add(65);
    ValueList.add(92);
    ValueList.add(18);
    ValueList.add(23);
    ValueList.add(26);
    ValueList.add(97);
    ValueList.add(67);
    ValueList.add(54);
    ValueList.add(34);

    Map<Object, Object> map1 = new LinkedHashMap<>();

    for (int i = 0; i < X_AxesList.size(); i++) {

        for (int j = 0; j < Y_AxesList.size(); j++) {

            for (int k = 0; k <ValueList.size(); k++) {

                map1.put("Country", X_AxesList.get(i));
                map1.put(Y_AxesList.get(j), ValueList.get(k));





                // System.out.println(X_AxesList.get(i));
                dataProviderList.add(map1);
            }
        }
    }
    Map<String, Object> responseMap = new LinkedHashMap<>();
    responseMap.put("dataProvider", dataProviderList);

    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.enable(SerializationFeature.INDENT_OUTPUT);

    String mapToJson = objectMapper.writeValueAsString(responseMap);
    System.out.println(mapToJson);
}

}

我希望输出如下：

"dataProvider": [{
  "country": "Arizona",
  "2012": 20,
  "2013": 30,
  "2014": 10,
  "2015": 40
}, {
  "country": "Arkansas",
  "2012": 50,
  "2013": 15,
  "2014": 35,
  "2015": 42
}, {
  "country": "Florida",
  "2012": 85,
  "2013": 19,
  "2014": 16,
  "2015": 65
}, {
  "country": "Ohio",
  "2012": 92,
  "2013": 18,
  "2014": 23,
  "2015": 26
}, {
  "Country": "WashingtonDC",
  "2012": 34,
  "2013": 54,
  "2014": 67,
  "2015": 21
}]

当我尝试在for循环中应用上述逻辑时，它给出了400次迭代的输出：

 [{
    "Country" : "WashingtonDC",
    "2012" : 34,
    "2013" : 34,
    "2014" : 34,
    "2015" : 34
  }, {
    "Country" : "WashingtonDC",
    "2012" : 34,
    "2013" : 34,
    "2014" : 34,
    "2015" : 34
  }, {
    "Country" : "WashingtonDC",
    "2012" : 34,
    "2013" : 34,
    "2014" : 34,
    "2015" : 34
  } ,{},{},{}............400]

但是我只需要5次迭代，如上面代码所示，通过使用arrayList和hashmap以及DYNAMICfor循环

请帮助我完成for循环逻辑部分。提前谢谢

Answer 1

您必须解决这些问题，不断向相同的Map添加值，以便最后一个键覆盖前面的键，并且您迭代值列表，而不是从中获取切片

用2替换3个嵌套的for循环，并使用索引跟踪ValueList

int valuesIndex = 0;
for (String country: X_AxesList) {
    Map<Object, Object> map1 = new LinkedHashMap<>();
    map1.put("Country", country);
    for (String year: Y_AxesList) {
        map1.put(year, ValueList.get(valuesIndex++));   
    }
    dataProviderList.add(map1);
}

输出

Country Arizona
2012 20
2013 30
2014 10
2015 40
Country Arkansas
2012 50
2013 15
2014 35
2015 42
Country Florida
2012 85
2013 19
2014 16
2015 65
Country Ohio
2012 92
2013 18
2014 23
2015 26
Country WashingtonDC
2012 97
2013 67
2014 54
2015 34