对HashMap的value做升序、降序

public class MapUtils {

    // Map的value值降序排序
    public static <K, V extends Comparable<? super V>> Map<K, V> sortDescend(Map<K, V> map) {
        List<Map.Entry<K, V>> list = new ArrayList<>(map.entrySet());
        list.sort((o1, o2) -> {
            int compare = (o1.getValue()).compareTo(o2.getValue());
            return -compare;
        });

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

    // Map的value值升序排序
    public static <K, V extends Comparable<? super V>> Map<K, V> sortAscend(Map<K, V> map) {
        List<Map.Entry<K, V>> list = new ArrayList<>(map.entrySet());
        list.sort(Map.Entry.comparingByValue());

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

}

因为结果要求是有序的，所以返回的类型必须是LinkedHashMap