计算一个 JSONArray 有多少特定的 JSONObjects答案

【问题标题】：Counting how many certain JSONObjects a JSONArray has计算一个 JSONArray 有多少特定的 JSONObjects
【发布时间】：2019-09-11 07:25:03
【问题描述】：

我正在尝试获取 JSONArray 的 JSONObjects 的数量。我的 JSONArray 就像

varArray: [{"value1_1_1":0},{"value1_2_2":0},{"value1_4_1":0},{"value1_5_3":0}, {"value1_8_3":0},{"value1_1_9":0},{"value1_2_6":0},{"value1_4_1":0},{"value1_5_7":0},{"value1_8_9":0},{"value1_1_1":0},{"value1_1_1":0},{"value1_2_6":0},{"value1_2_6":0},{"value1_3_5":0},{"value1_3_5":0},{"value1_4_2":0},{"value1_4_2":0},{"value1_8_6":0},{"value1_8_6":0},{"value1_10_5":0},{"value1_10_5":0}];

我想用 JSONObject 的编号替换那些 '0'。想要的结果是

varArray: [{"value1_1_1":3},{"value1_2_2":1},{"value1_4_1":2},{"value1_5_3":1}, {"value1_8_3":1},{"value1_1_9":1},{"value1_2_6":3},{"value1_5_7":1},{"value1_8_9":1},{"value1_3_5":2},{"value1_4_2":2},{"value1_8_6":2},{"value1_10_5":2}];

我尝试了类似下面的方法但失败了。

    JSONArray newArray = new JSONArray();
    for(int i=0;i<varArray.size();i++){

            JSONObject jsonFromArr = varArray.getJSONObject(i);


            for(int a=1;a<=order1Max;a++){
                for(int b=1;b<=order2Max;b++){
                    for(int c=1;c<=valueMax;c++){
                        if(jsonFromArr.get("value"+a+"_"+b+"_"+c) != null){
                            jsonArrayList.add(jsonFromArr.toString());

                            if(!newArray.contains(jsonFromArr)){
                                newArray.add(jsonFromArr);

                            } else{
                                // I can't figure out what to do here.
                            }
                        }
                    }
                }
            }
        }

我认为结果应该计入循环，因为 JSONObject 的键是动态的。如何获得我想要的结果？

---已编辑

完整代码（替换一些必须搜索数据库的部分）

JSONArray varArray = [{"value1_1_1":0},{"value1_2_2":0},{"value1_4_1":0},{"value1_5_3":0},{"value1_8_3":0},{"value1_1_9":0},{"value1_2_6":0},{"value1_4_1":0},{"value1_5_7":0},{"value1_8_9":0},{"value1_1_1":0},{"value1_1_1":0},{"value1_2_6":0},{"value1_2_6":0},{"value1_3_5":0},{"value1_3_5":0},{"value1_4_2":0},{"value1_4_2":0},{"value1_8_6":0},{"value1_8_6":0},{"value1_10_5":0},{"value1_10_5":0}];

JSONArray newArray = new JSONArray();
for(int i=0;i<varArray.size();i++){
    JSONObject jsonFromArr = varArray.getJSONObject(i);
    for(int a=1;a<=1;a++){
        for(int b=1;b<=10;b++){
            for(int c=1;c<=9;c++){
                if(jsonFromArr.get("value"+a+"_"+b+"_"+c) != null){
                    if(!newArray.contains(jsonFromArr)){
                       newArray.add(jsonFromArr);
                    } else{
                        // I can't figure out what to do here.
                    }
                }
            }
        }
    }
}

【问题讨论】：

我会用一个简单的Map<String, int>
@Yoojin Kim 你能把你的整个代码贴在这里吗？我想在本地运行它并对其进行更改。

标签： java arrays json for-loop

【解决方案1】：

一种简单的方法是将给定的 json 数组转换为Map<String, Integer>，如countMap。然后将countMap转化为json对象。

public static void main(String[] args) {
    String jsonStr = "[{\"value1_1_1\":0},{\"value1_2_2\":0},{\"value1_4_1\":0},{\"value1_5_3\":0},{\"value1_8_3\":0},{\"value1_1_9\":0},{\"value1_2_6\":0},{\"value1_4_1\":0},{\"value1_5_7\":0},{\"value1_8_9\":0},{\"value1_1_1\":0},{\"value1_1_1\":0},{\"value1_2_6\":0},{\"value1_2_6\":0},{\"value1_3_5\":0},{\"value1_3_5\":0},{\"value1_4_2\":0},{\"value1_4_2\":0},{\"value1_8_6\":0},{\"value1_8_6\":0},{\"value1_10_5\":0},{\"value1_10_5\":0}]";

    Map<String, Integer> countMap = new HashMap<>();
    JSONArray jsonArray = new JSONArray(jsonStr);
    for (int i = 0; i < jsonArray.length(); i++) {
        String name = JSONObject.getNames(jsonArray.getJSONObject(i))[0];
        if (countMap.containsKey(name)) {
            countMap.put(name, countMap.get(name)+1);
        } else {
            countMap.put(name, 1);
        }
     }
     System.out.println(countMap.toString());

     JSONArray jsonArrayNew = new JSONArray();
     countMap.forEach((k, v) -> {
         JSONObject jsonObj = new JSONObject();
         jsonArrayNew.put(jsonObj.put(k, v));
     });
     System.out.println(jsonStrNew.toString());
}

控制台输出：

{value1_8_6=2, value1_8_9=1, value1_4_2=2, value1_5_3=1, value1_2_6=3, value1_3_5=2, value1_1_9=1, value1_8_3=1, value1_5_7=1, value1_1_1=3, value1_2_2=1, value1_4_1=2, value1_10_5=2}
[{"value1_10_5":2},{"value1_1_1":3},{"value1_1_9":1},{"value1_2_2":1},{"value1_2_6":3},{"value1_3_5":2},{"value1_4_1":2},{"value1_4_2":2},{"value1_5_3":1},{"value1_5_7":1},{"value1_8_3":1},{"value1_8_6":2},{"value1_8_9":1}]

【讨论】：

【解决方案2】：

您想要的是计算唯一键 valueX_Y_Z 的出现次数。这可以使用 Java8 流作为 for 循环的替代方案来完成。

public static void main(String[] args) {
    String json = "[{\"value1_1_1\":0},{\"value1_2_2\":0},{\"value1_4_1\":0},{\"value1_5_3\":0},{\"value1_8_3\":0},{\"value1_1_9\":0},{\"value1_2_6\":0},{\"value1_4_1\":0},{\"value1_5_7\":0},{\"value1_8_9\":0},{\"value1_1_1\":0},{\"value1_1_1\":0},{\"value1_2_6\":0},{\"value1_2_6\":0},{\"value1_3_5\":0},{\"value1_3_5\":0},{\"value1_4_2\":0},{\"value1_4_2\":0},{\"value1_8_6\":0},{\"value1_8_6\":0},{\"value1_10_5\":0},{\"value1_10_5\":0}]";

    JSONArray jsonArray = new JSONArray(json);

    List<JSONObject> jsonObjects = arrayToStream(jsonArray)
            .map(JSONObject.class::cast)
            // get a stream of valuex_y_z
            .map(jo -> JSONObject.getNames(jo)[0]) 
            // collect into a Map<String, Long>, each key is a unique "valuex_y_z"
            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting())) 
            // stream map entries
            .entrySet().stream()
            // build a stream of JSONObject
            .map(e -> new JSONObject().put(e.getKey(), e.getValue()))
            // collect to a list
            .collect(Collectors.toList());

    // build new JSONArray 
    JSONArray jsonArrayGroupBy = new JSONArray(jsonObjects);

    System.out.println(jsonArrayGroupBy.toString());
}

private static Stream<Object> arrayToStream(JSONArray array) {
    return StreamSupport.stream(array.spliterator(), false);
}

【讨论】：