java map 根據value排序取前n

package com.cnblogs.test;

import java.util.List;
import java.util.Map;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

/**
 * @author toutou 2019/03/17
 */
public class Java8future {

    public static void main(String[] args) {
        Map<String, Integer> map = ImmutableMap.of("gq", 7, "aa", 9, "zs", 66, "vv", 3);
        System.out.println("原始的map：" + map);
        System.out.println("key降序：" + sortByKey(map, true, 2));
        System.out.println("key升序：" + sortByKey(map, false, 2));
        System.out.println("value降序：" + sortByValue(map, true, 2));
        System.out.println("value升序：" + sortByValue(map, false, 2));
    }

    /**
     * Sort map by value
     *
     * @param map map source
     * @param isDesc 是否降序，true：降序，false：升序
     * @param limit 取前幾條
     * @return 已排序map
     */
    public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map, boolean isDesc, int limit) {
        Map<K, V> result = Maps.newLinkedHashMap();
        if (isDesc) {
            map.entrySet().stream().sorted(Map.Entry.<K, V>comparingByValue().reversed()).limit(limit)
                    .forEach(e -> result.put(e.getKey(), e.getValue()));
        } else {
            map.entrySet().stream().sorted(Map.Entry.<K, V>comparingByValue())
                    .forEachOrdered(e -> result.put(e.getKey(), e.getValue()));
        }
        return result;
    }

    /**
     * Sort map by key
     *
     * @param map 待排序的map
     * @param isDesc 是否降序，true：降序，false：升序
     * @param limit 取前幾條
     * @return 已排序map
     */
    public static <K extends Comparable<? super K>, V> Map<K, V> sortByKey(Map<K, V> map, boolean isDesc, int limit) {
        Map<K, V> result = Maps.newLinkedHashMap();
        if (isDesc) {
            map.entrySet().stream().sorted(Map.Entry.<K, V>comparingByKey().reversed()).limit(limit)
                    .forEachOrdered(e -> result.put(e.getKey(), e.getValue()));
        } else {
            map.entrySet().stream().sorted(Map.Entry.<K, V>comparingByKey())
                    .forEachOrdered(e -> result.put(e.getKey(), e.getValue()));
        }
        return result;
    }
}