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import java.util.*;
/**
* @author HavenTong
* @date 2020/3/5 5:34 下午
*/
public class MapUtil {
public static void show(Map<String, Integer> map) {
for (Map.Entry<String, Integer> entry: map.entrySet()) {
System.out.println(entry.getKey() + " " + entry.getValue());
}
System.out.println("=======================");
System.out.println();
}
/**
* 获取按照value升序排序后的map
* @param map 需要排序的map
* @return 排好序的map
*/
public static Map<String, Integer> sortByValueAsc(Map<String, Integer> map) {
List<Map.Entry<String, Integer>> list = new ArrayList<>(map.entrySet());
// 升序
Collections.sort(list, (e1, e2) -> e1.getValue().compareTo(e2.getValue()));
Map<String, Integer> sortedMap = new LinkedHashMap<>();
for (Map.Entry<String, Integer> entry: list) {
sortedMap.put(entry.getKey(), entry.getValue());
}
return sortedMap;
}
/**
* 获取按照value降序排序后的map
* @param map 需要排序的map
* @return 排好序的map
*/
public static Map<String, Integer> sortByValueDesc(Map<String, Integer> map) {
List<Map.Entry<String, Integer>> list = new ArrayList<>(map.entrySet());
// 降序
Collections.sort(list, (e1, e2) -> e2.getValue().compareTo(e1.getValue()));
Map<String, Integer> sortedMap = new LinkedHashMap<>();
for (Map.Entry<String, Integer> entry: list) {
sortedMap.put(entry.getKey(), entry.getValue());
}
return sortedMap;
}
/**
* 通过TreeMap的方式对key按照升序排序
* @param map 要排序的map
* @return 按照key升序排好序的map
*/
public static Map<String, Integer> sortByKeyByTreeMapAsc(Map<String, Integer> map) {
/*
The naturalOrder() method of Comparator Interface in Java
returns a comparator that use to compare Comparable objects in natural order.
*/
Map<String, Integer> sortedMap = new TreeMap<>(Comparator.naturalOrder());
sortedMap.putAll(map);
return sortedMap;
}
/**
* 通过TreeMap的方式对key按照将序排序
* @param map 要排序的map
* @return 按照key降序排好序的map
*/
public static Map<String, Integer> sortByKeyByTreeMapDesc(Map<String, Integer> map) {
/*
The reverseOrder() Returns a comparator that imposes the reverse of the natural ordering.
*/
Map<String, Integer> sortedMap = new TreeMap<>(Comparator.reverseOrder());
sortedMap.putAll(map);
return sortedMap;
}
public static void main(String[] args) {
Map<String, Integer> map = new HashMap<>();
map.put("boss", 2);
map.put("abuse", 1);
map.put("unit", 3);
map.put("duty", 4);
// 根据Value升序排序
System.out.println("🚀 SORT BY VALUE ASC:");
Map<String, Integer> sortedMapAsc = sortByValueAsc(map);
show(sortedMapAsc);
// 根据Value降序排序
System.out.println("🚀 SORT BY VALUE DESC");
Map<String, Integer> sortedMapDesc = sortByValueDesc(map);
show(sortedMapDesc);
// 根据Key升序排序，使用TreeMap方式
System.out.println("🚀 SORT BY KEY ASC");
Map<String, Integer> sortedByKeyAsc = sortByKeyByTreeMapAsc(map);
show(sortedByKeyAsc);
// 根据Key降序排序，使用TreeMap方式
System.out.println("🚀 SORT BY KEY DESC");
Map<String, Integer> sortedByKeyDesc = sortByKeyByTreeMapDesc(map);
show(sortedByKeyDesc);
}
}
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