Compare two hashmaps in java for equal key values

Question

I have two maps:

Map1.put(a,1)
Map1.put(b,2)
Map1.put(c,3)
Map1.put(d,4)

Map2.put(a,1)
Map2.put(b,5)
Map2.put(c,3)
Map2.put(d,4)
Map2.put(e,6)
Map2.put(f,9)

How do I compare Map1 and Map2 for equal key values? If the key is not matching in Map2 then ignore that key.

Extract the key sets from each map and use the methods outlined in https://stackoverflow.com/q/3341202/13075. — Henrik Aasted Sørensen, Aug 16 '17 at 14:06
Possible duplicate of [What is the fastest way to compare two sets in Java?](https://stackoverflow.com/questions/3341202/what-is-the-fastest-way-to-compare-two-sets-in-java) — Ori Marko, Aug 16 '17 at 14:10

score 3 · Answer 1 · edited Oct 11 '21 at 08:09

get the keySet() of every map and use the ContainsAll() method

Map<String, Integer> Map1 = new HashMap<>();
Map1.put("a", 1);
Map1.put("b", 2);
Map1.put("c", 3);
Map1.put("d", 4);

Map<String, Integer> Map2 = new HashMap<>();
Map2.put("a", 1);
Map2.put("b", 5);
Map2.put("c", 3);
Map2.put("d", 4);
Map2.put("e", 6);
Map2.put("f", 9);

// check if all keys from Map1 are present in Map2
System.out.println(Map2.keySet().containsAll(Map1.keySet()));

score 1 · Answer 2 · edited Oct 10 '21 at 11:28

Try intersection() with Entries. It will check keys and values and return common entries.

Map<String, Integer> map1 = new HashMap<>();
map1.put("a", 1);
map1.put("b", 2);
map1.put("c", 3);
map1.put("d", 4);

Map<String, Integer> map2 = new HashMap<>();
map2.put("a", 2);
map2.put("b", 3);
map2.put("c", 4);
map2.put("d", 5);
map2.put("e", 6);
map2.put("f", 9);

Collection<Map.Entry<String, Integer>> commonValues = CollectionUtils.intersection(map1.entrySet(), map2.entrySet());

System.out.println(CollectionUtils.isEmpty(commonValues)); // if empty, then no same key and value found.

For keys alone use :

Collection<String> commonKeys = CollectionUtils.intersection(map1.keySet(), map2.keySet());

nagendra547 · Answer 3 · 2021-11-19T08:57:59.513

0

This is another simple solution.

Map1.keySet().retainAll(Map2.keySet());

Map1.keySet() contains only keys in both sets

edited Nov 19 '21 at 08:57

answered Aug 16 '17 at 16:05

nagendra547

5,672
3
29
43

Compare two hashmaps in java for equal key values

3 Answers3