返回一个新映射，其中包含输入映射的所有项，但值为空的项除外。

/**
 from
* N o w J a v a . c o m - 时代Java 
**/

//package com.nowjava;


import java.util.HashMap;


import java.util.Map;


public class Main {

    /**

     * Returns a new map with all entries of the input map except those which have a value of null.<p>

     * 

     * @param <A> the key type of the map

     * @param <B> the value type of the map 

     * @param map the input map

     *  

     * @return a map with all null entries removed 

     */

    public static <A, B> Map<A, B> removeNullEntries(Map<A, B> map) {


        HashMap<A, B> result = new HashMap<A, B>();


        for (Map.Entry<A, B> entry : map.entrySet()) {

            if (entry.getValue() != null)