Comparing two hash-maps and printing intersections

Question

I have two hash maps: one contains an Integer key and String value.

The other contains an Integer key and float value.

Code

Map<Integer,String> mapA = new HashMap<>();
mapA.put(1, "AS");
mapA.put(2, "Wf");

Map<Integer,Float> mapB = new HashMap<>();
mapB.put(2, 5.0f);
mapB.put(3, 9.0f);

My question is how to compare the two hash maps using the integer key value? I want to print the bitmap value when the key values are the same.

Answer 1

You can just iterate on the keys of mapA and check if it is present in mapB then add the value to a third mapC for example.

Map<String, float> mapC = new HashMap<String, float>();

for (Integer key : mapA.keySet()) {
    if (mapB.containsKey(key)) {
        mapC.put(mapA.get(key), mapB.get(key));
    }
}

Answer 2

Compare keys in two map by using mapB iterator.

Iterator<Entry<Integer, Float>> iterator = mapB.entrySet().iterator();
    while(iterator.hasNext()) {
        Entry<Integer, Float> entry = iterator.next();
        Integer integer = entry.getKey();
        if(mapA.containsKey(integer)) {
            System.out.println("Float Value : " + entry.getValue());
        }
    }

Answer 3

If you are allowed to modify mapB , then the solution is as simple as mapB.keySet().retainAll(mapA.keySet()); .

This will only leave those entries in mapB that have a corresponding key in mapA , because the set returned by keySet() is backed by the map itself, any changes made to it will be reflected to the map.

Answer 4

yes i got solution...

 if(mapB.containsKey(position)){
          Log.e("bucky",mapB.get(position));}

position means integer value.

Answer 5

With Java 8 Streams API:

Map<Integer, Object> matchInBothMaps = mapA
                                            .entrySet()
                                            .stream() 
                                            .filter(map -> mapB.containsKey(map.getKey())) 
                                            .collect(Collectors.toMap(map -> map.getKey(), 
                                                                      map -> map.getValue()));
        
System.out.println(matchInBothMaps);