Check whether a map contains all contents of another map

Question

I am trying to check whether a map contains all contents of another map. For example, I have a mapA which is a Map<String, List<String>> and the elements are:

"1" -> ["a","b"]
"2" -> ["c","d"]

another mapB which is also a Map<String, List<String>>, the elements are:

"1" -> ["a"]
"2" -> ["c","d"],

I want to create a function compare(mapA, mapB) which will return false in this case.

What is the best way to do this?

Pogge

Just for your future self's sanity, don't call it compare. You are not comparing. Call it something like containsAll or subsumes. – Apprehension

Answer 1

Inside your compare(mapA, mapB) method, you can simply use:

return mapA.entrySet().containsAll(mapB.entrySet());

Backbreaker

But will this also check for values? If no, what's a better way to check for both key and values? – Selfcongratulation

@Selfcongratulation I'm not sure why I never responded to your comment, but yes, this will check for the existence of all entries in mapB within mapA. An entry consists of both a key and a value, and entry equality is determined by both the key being equal and the value being equal. – Backbreaker

Answer 2

Try this code :

Assert.assertTrue(currentMap.entrySet().containsAll(expectedMap.entrySet()));

Held

Answer 3

The answer provided by @Jacob G wont work in your case. It will work only if there is an extra (key, value) pair in MapA. like

MapA = {"1" -> ["a","b"] "2" -> ["c","d"] } 

and

MapB = {"1" -> ["a","b"]  }. 

What you need is this:

boolean isStrictlyDominate(LinkedHashMap<Integer, HashSet<Integer>> firstMap, LinkedHashMap<Integer, HashSet<Integer>> secondMap){
    for (Map.Entry<Integer, HashSet<Integer>> item : secondMap.entrySet()) {
        int secondMapKey = item.getKey();
        if(firstMap.containsKey(secondMapKey)) {
            HashSet<Integer> secondMapValue = item.getValue();
            HashSet<Integer> firstMapValue = firstMap.get(secondMapKey) ;
            if(!firstMapValue.containsAll(secondMapValue)) {
                return false;
            }

        }
    }
    return !firstMap.equals(secondMap);
}

(if you do not want to check strict domination then just return true at last return statement)

Fissure

Answer 4

you can try this.

static boolean compare(Map<String, List<String>> mapA, Map<String, List<String>> mapB){
        return mapA.entrySet().containsAll(mapB.entrySet());
    }

As suppose, provided data is something like this:

            Map<String, List<String>> mapA = new HashMap<>();
            Map<String, List<String>> mapB = new HashMap<>();

            mapA.put("1", Arrays.asList("a","b"));
            mapA.put("2", Arrays.asList("c","d"));

            mapB.put("1", Arrays.asList("a"));
            mapB.put("2", Arrays.asList("c", "d"));

            System.out.println(compare(mapA, mapB));

In this case compare(mapA, mapB) method will return false. But suppose provided data is something like this:

            Map<String, List<String>> mapA = new HashMap<>();
            Map<String, List<String>> mapB = new HashMap<>();

            mapA.put("1", Arrays.asList("a","b"));
            mapA.put("2", Arrays.asList("c","d"));

            mapB.put("1", Arrays.asList("a", "b"));
            mapB.put("2", Arrays.asList("c", "d"));

            System.out.println(compare(mapA, mapB));

In this case, compare(mapA, mapB) method, which I have written will return true.

compare(mapA, mapB) method basically checking for all the entries in mapA with mapB, if same returning yes, else returning false;

Gitlow