java8 实现map以value值排序操作

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.LinkedHashMap;
 
public class MapSorted{
 
 public static void main(String[] args) {
  
  Map<String, Integer> map = new HashMap<>();
  map.put("A", 3);
  map.put("B", 5);
  map.put("C", 1);
  map.put("D", 1);
  map.put("E", 9);
  
  System.out.println(map);
 
  //如果value为java对象，则需要实现Comparable接口，重写compareTo方法
 
  Map<String, Integer> sortedMap = new LinkedHashMap<>();
  Map<String, Integer> sortedMap2 = new LinkedHashMap<>();
 
  //ASC
  map.entrySet().stream()
   .sorted(Map.Entry.<String, Integer>comparingByValue())
   .forEachOrdered(x -> sortedMap.put(x.getKey(), x.getValue()));
 
  System.out.println(sortedMap);
 
  //DESC Collections.reverseOrder || reversed()
  map.entrySet().stream()
  .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
  .forEachOrdered(x -> sortedMap2.put(x.getKey(), x.getValue()));
 
  // map.entrySet().stream()
  // .sorted(Map.Entry.<String, Integer>comparingByValue().reversed())
  // .forEachOrdered(x -> sortedMap2.put(x.getKey(), x.getValue()));
 
  System.out.println(sortedMap2);
 
  //Collectors.toMap 直接返回排好序的map
  map = map.entrySet().stream()
     .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
     .collect(Collectors.toMap(x -> x.getKey(), x -> x.getValue(), (x1, x2) -> x2, LinkedHashMap::new));
  
  // map = map.entrySet().stream()
  // .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
  // .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (x1, x2) -> x2, LinkedHashMap::new));
  System.out.println(map);
 }
}

{A=3, B=5, C=1, D=1, E=9}
{C=1, D=1, A=3, B=5, E=9}
{E=9, B=5, A=3, C=1, D=1}
{E=9, B=5, A=3, C=1, D=1}

　　/**
   * 
   * Map根据value排序;
   * 
   * @param map
   * @return
   */
  public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
    List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
    Collections.sort(list, new Comparator<Map.Entry<K, V>>() {
      @Override
      public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) {
        return (o2.getValue()).compareTo(o1.getValue());
      }
    });

    Map<K, V> result = new LinkedHashMap<>();
    for (Map.Entry<K, V> entry : list) {
      result.put(entry.getKey(), entry.getValue());
    }
    return result;
  }

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
    List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
    
    list.sort(Comparator.comparing(Entry::getValue));

    Map<K, V> result = new LinkedHashMap<>();
    for (Map.Entry<K, V> entry : list) {
      result.put(entry.getKey(), entry.getValue());
    }
    return result;
  }

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
    List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
    
    list.sort((o1, o2)-> o2.getValue().compareTo(o1.getValue()));

    Map<K, V> result = new LinkedHashMap<>();
    for (Map.Entry<K, V> entry : list) {
      result.put(entry.getKey(), entry.getValue());
    }
    return result;
  }

 public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
    List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
    
    list.sort((o1, o2)-> o2.getValue().compareTo(o1.getValue()));

    Map<K, V> result = new LinkedHashMap<>();
    list.stream().forEach(entry -> result.put(entry.getKey(), entry.getValue()));
    
    return result;
  }

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
    Map<K, V> sortMap = new LinkedHashMap<>();
    new map.entrySet().stream()
        .sorted((o1, o2) -> o2.getValue().compareTo(o1.getValue()))
        .forEach(entry -> sortMap.put(entry.getKey(), entry.getValue()));
    return sortMap;
  }

  /**
   * flag = 1 正序
   * flag = 0 倒序
   * @param map
   * @param flag
   * @return
   */
  public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map, int flag) {
    Map<K, V> sortMap = new LinkedHashMap<>();
    if(flag == 1) {
      map.entrySet().stream()
      .sorted((o1, o2) -> o1.getValue().compareTo(o2.getValue()))
      .forEach(entry -> sortMap.put(entry.getKey(), entry.getValue()));
    } else {
      map.entrySet().stream()
      .sorted((o1, o2) -> o2.getValue().compareTo(o1.getValue()))
      .forEach(entry -> sortMap.put(entry.getKey(), entry.getValue()));
    }
    return sortMap;
  }

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue2(Map<K, V> map, int flag) {
    
    if(flag == 1) {
      return map.entrySet().stream().sorted((o1, o2) -> o1.getValue().compareTo(o2.getValue())).map(entry -> {
        Map<K, V> result = new LinkedHashMap<>();
        result.put(entry.getKey(), entry.getValue());
        return result;
      }).reduce((map1, map2) -> {
        map2.entrySet().forEach(entry -> map1.put(entry.getKey(), entry.getValue()));
        return map1;
      }).get();
    } else {
      return map.entrySet().stream().sorted((o1, o2) -> o2.getValue().compareTo(o1.getValue())).map(entry -> {
        Map<K, V> result = new LinkedHashMap<>();
        result.put(entry.getKey(), entry.getValue());
        return result;
      }).reduce((map1, map2) -> {
        map2.entrySet().forEach(entry -> map1.put(entry.getKey(), entry.getValue()));
        return map1;
      }).get();
      
    }