How to receive difference of maps in java?

Question

I have two maps:

Map map1;
Map map2;

I need to receive difference between these maps. Does exist ma

Answer 1

Building on Vlad's example to work with maps of different sizes

public static <K, V> Map<K, V> mapDiff(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(left.size() <= right.size() ? left.entrySet() : right.entrySet());

        return difference;
    }

Answer 2

Try using guava's MapDifference.

Answer 3

Simple way to do it. if you want complex way, you can change filter to compare value.

    Map<String, Object> map1 = new HashMap<String, Object>() {{
        put("A", "1");
        put("B", "2");
        put("C", "3");
    }};
    Map<String, Object> map2 = new HashMap<String, Object>() {{
        put("A", "1");
        put("B", "2");
        put("D", "3");
    }};
    Map<String, Object> newList = map1.keySet().stream().filter(str -> !map2.containsKey(str)).collect(Collectors.toMap(v -> v, v -> map1.get(v)));
    Map<String, Object> oldList = map2.keySet().stream().filter(str -> !map1.containsKey(str)).collect(Collectors.toMap(v -> v, v -> map2.get(v)));

    System.out.println(newList);
    System.out.println(oldList);

Answer 4

    Set<Entry<String, Object>> diff = new HashSet<Entry<String, Object>>((map1.entrySet()));
    diff.addAll(map2.entrySet());//Union
    Set<Entry<String, Object>> tmp = new HashSet<Entry<String, Object>>((map1.entrySet()));
    tmp.retainAll(map2.entrySet());//Intersection
    diff.removeAll(tmp);//Diff

Answer 5

How about google guava?:

Maps.difference(map1,map2)

Answer 6

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