map集合取并集，差集，交集

前段时间需要用到取两个集合的并集，差集，交集，在这贴下代码记录一下

1.获取两个map的并集

/**
 * 取Map集合的并集
 *
 * @param map1 大集合
 * @param map2 小集合
 * @return 两个集合的并集
 */
public static Map getUnionSetByGuava(Map map1, Map map2) {
    Set bigMapKey = map1.keySet();
    Set smallMapKey = map2.keySet();
    Set differenceSet = Sets.union(bigMapKey, smallMapKey);
    Map result = Maps.newHashMap();
    for (String key : differenceSet) {
        if (map1.containsKey(key)) {
            result.put(key, map1.get(key));
        } else {
            result.put(key, map2.get(key));
        }
    }
    return result;
}

2.获取两个map差集

/**
 * 取Map集合的差集
 *
 * @param bigMap   大集合
 * @param smallMap 小集合
 * @return 两个集合的差集
 */
public static Map getDifferenceSetByGuava(Map bigMap, Map smallMap) {
    Set bigMapKey = bigMap.keySet();
    Set smallMapKey = smallMap.keySet();
    Set differenceSet = Sets.difference(bigMapKey, smallMapKey);
    Map result = Maps.newHashMap();
    for (String key : differenceSet) {
        result.put(key, bigMap.get(key));
    }
    return result;
}

3.获取连个map交集

/**
 * 取Map集合的交集（String,String）
 *
 * @param map1 大集合
 * @param map2 小集合
 * @return 两个集合的交集
 */
public static Map getIntersectionSetByGuava(Map map1, Map map2) {
    Set bigMapKey = map1.keySet();
    Set smallMapKey = map2.keySet();
    Set differenceSet = Sets.intersection(bigMapKey, smallMapKey);
    Map result = Maps.newHashMap();
    for (String key : differenceSet) {
        result.put(key, map1.get(key));
    }
    return result;
}