Compare two maps for keys and return boolean

Question

I have two maps and I need to check if both has the same keys and same number of keys or not and return a boolean. I would like to use streams for this and I have got is by creating another list

mapA
.entrySet()
.stream()
.filter(entry -> mapB.containsKey(entry.getKey()))
.collect(
    Collectors.toMap(Entry::getKey, Entry::getValue));

But my question is that can I do it in a single line that would not create another list but return a boolean whether if they are same or not.

@Andronicus Yes if both maps have same keys and same number of keys then i need to return true else false — NewUser
– NewUser, Commented Mar 25, 2019 at 20:11
@YCF_L Thanks I would need to check if the number of keys is also same in both the maps — NewUser
– NewUser, Commented Mar 25, 2019 at 20:12
@YCF_L If mapA has additional keys that mapB doesn't have, containsAll will still return true. That's not what OP wants. — GrandOpener
– GrandOpener, Commented Mar 25, 2019 at 20:44

Ryuzaki L · Accepted Answer · 2019-03-25 20:19:35Z

5

There's no need to use streams for this. Just obtain the maps' key sets and use equals, which is specified in Set as follows:

Returns true if the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set [.]

Map<String, Integer> m1 = new HashMap<>();
m1.put("a", 10);
m1.put("b", 10);
m1.put("c", 10);

Map<String, Integer> m2 = new HashMap<>();
m2.put("c", 20);
m2.put("b", 20);
m2.put("a", 20);

System.out.println(m1.keySet().equals(m2.keySet()));  //true

edited Mar 25, 2019 at 20:19

Ryuzaki L

40.4k14 gold badges81 silver badges111 bronze badges

answered Mar 25, 2019 at 20:12

rgettman

179k30 gold badges282 silver badges365 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Compare two maps for keys and return boolean

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related