java Map根據value排序

轉自：https://www.cnblogs.com/binz/p/6671917.html

• 通用方式

public class MapUtil {
    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.Entry<K, V>>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<K, V>>() {
            public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) {
                //遞增排序，如果o1和o2互換位置，就變成遞減排序
                return (o1.getValue()).compareTo(o2.getValue());
            }
        });
 
        Map<K, V> result = new LinkedHashMap<K, V>();
        for (Map.Entry<K, V> entry : list) {
            result.put(entry.getKey(), entry.getValue());
        }
        return result;
    }
}

• java8

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
       Map<K, V> result = new LinkedHashMap<>();
       Stream<Entry<K, V>> st = map.entrySet().stream();
 
       st.sorted(Comparator.comparing(e -> e.getValue())).forEach(e -> result.put(e.getKey(), e.getValue()));
 
       return result;
   }