java map差集，并集

public static void getDifferenceSetByGuava(Map<String, Object> bigMap, Map<String, String> smallMap, Map<String, Object> resMap) {
    Set<String> bigMapKey = bigMap.keySet();
    Set<String> smallMapKey = smallMap.keySet();
    Set<String> differenceSet = Sets.difference(bigMapKey, smallMapKey);//差集

Set<String> differenceSet = Sets.union(bigMapKey, smallMapKey);//并集

for (String key : differenceSet)
 { 
resMap.put(key, bigMap.get(key)); } 
}