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Map根据key排序

1.第一种方法

首先定义好一个传key的比较器对象来构造TreeMap

        Map<String,Object> mapping = new TreeMap<>(new MyComparator());
        mapping.put("afieldName","特征名称");
        mapping.put("std","方差");
        mapping.put("min","最小值");
        mapping.put("avg","平均值");
        mapping.put("nanCount","缺失值");
        mapping.put("max","最大值");
        mapping.put("skewness","偏度");
        mapping.put("kurtosis","峰度");
        mapping.put("standardDeviation","标准差");
        System.out.println("mapping="+mapping);
     
定义key的比较器
class MyComparator implements Comparator<String> {
    public int compare(String o1, String o2) {
        return o1.compareTo(o2);
    }
}

1.第二种方法

Map先存放数据,之后再进行排序

Map根据key的值进行排序
    /**
     * Map根据key的值进行排序
     *
     * @param map
     * @return
     */
    public static Map<String,Object> sortMapByKey(Map<String,Object> map){
        List<Map.Entry<String,Object>> entryList = new ArrayList<>(map.entrySet());
        entryList.sort(Comparator.comparing(o-> o.getKey()));
        //遍历排序好的list,一定要放进LinkedHashMap,因为只有LinkedHashMap是根据插入顺序进行存储
        LinkedHashMap<String,Object> linkedHashMap = new LinkedHashMap<>();
        for(Map.Entry<String,Object> entry : entryList){
            linkedHashMap.put(entry.getKey(),entry.getValue());
        }
        return linkedHashMap;
    }
Map根据value的值进行排序
   /**
     * Map根据value的值进行排序
     *
     * @param map
     * @return
     */
    public static Map<String,Object> sortMapByValue(Map<String,Object> map){
        List<Map.Entry<String,Object>> entryList = new ArrayList<>(map.entrySet());
        entryList.sort(Comparator.comparing(o-> o.getValue().toString()));
        //遍历排序好的list,一定要放进LinkedHashMap,因为只有LinkedHashMap是根据插入顺序进行存储
        LinkedHashMap<String,Object> linkedHashMap = new LinkedHashMap<>();
        for(Map.Entry<String,Object> entry : entryList){
            linkedHashMap.put(entry.getKey(),entry.getValue());
        }
        return linkedHashMap;
    }

进行代码测试

定义Map测试
    public static void main(String[] args) {
        //传进来一个key的比较器对象来构造treemap
        Map<String,Object> mapping = new TreeMap<>();
        mapping.put("fieldName","特征名称");
        mapping.put("std","方差");
        mapping.put("min","最小值");
        mapping.put("avg","平均值");
        mapping.put("nanCount","缺失值");
        mapping.put("max","最大值");
        mapping.put("skewness","偏度");
        mapping.put("kurtosis","峰度");
        mapping.put("standardDeviation","标准差");
        System.out.println("-------------1-------------");

        //按key排序
        Map<String,Object> objectMapKey = sortMapByKey(mapping);
        System.out.println(objectMapKey);
        System.out.println("-------------2-------------");

 		//按value排序
        Map<String,Object> objectMap = sortMapByValue(mapping);
        System.out.println(objectMap);
    }