Map根据key或value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 {

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);
}