How to receive difference of maps in java?

How about google guava?:

Maps.difference(map1,map2)

Here is a simple snippet you can use instead of massive Guava library:

public static <K, V> Map<K, V> mapDifference(Map<? extends K, ? extends V> left, Map<? extends K, ? extends V> right) {
    Map<K, V> difference = new HashMap<>();
    difference.putAll(left);
    difference.putAll(right);
    difference.entrySet().removeAll(right.entrySet());
    return difference;
}

Check out the whole working example