CODEWITHSUNDEEP
javahashmapkey
Sheikh Rahman
Sheikh Rahman

Reputation: 915

Java from 2 hashmap print key for which value does not match

The code below does not work. What logic can I use to print the key Job which has 2 different values in 2 hash maps?

public void randomTest() throws IOException {

        HashMap<String, String> map1 = new HashMap<>();
        HashMap<String, String> map2 = new HashMap<>();

        map1.put("Name", "Jones");
        map1.put("Job", "QAE");

        map2.put("Name", "Jones");
        map2.put("Job", "Developer");

        // ArrayList<String> ar = new ArrayList<>();
        Set<String> hs = new HashSet<>();
        for (Map.Entry<String, String> mm1 : map1.entrySet()) {
            hs.add(mm1.getValue());
        }
        for (Map.Entry<String, String> mm2 : map1.entrySet()) {
            hs.add(mm2.getValue());
        }

        for(String s: hs){
            System.out.println(s);
        }
       /* for (Map.Entry<String, String> mm1 : map1.entrySet()) {
            for(String str: hs){
               if(str.equals(mm1.getValue())){
                   System.out.println(mm1.getKey());
               }
            }
        }*/

    }

Expected output: Job.

Thanks in advance for your time.

Upvotes: 0

Views: 1156

Answers (3)

Anonymous
Anonymous

Reputation: 86343

This logic does the job (no pun intended).

    HashMap<String, String> map1 = new HashMap<>();
    HashMap<String, String> map2 = new HashMap<>();

    map1.put("Name", "Jones");
    map1.put("Job", "QAE");

    map2.put("Name", "Jones");
    map2.put("Job", "Developer");

    Set<String> hs = new HashSet<>();
    for (Map.Entry<String, String> mm1 : map1.entrySet()) {
        String map2Value = map2.get(mm1.getKey());
        if (! Objects.equals(mm1.getValue(), map2Value)) {
            hs.add(mm1.getKey());
        }
    }

    for(String s: hs){
        System.out.println(s);
    }

Output:

Job

I have added a comparison of the values from the two maps. Furthermore I am doing hs.add(mm1.getKey()); instead of hs.add(mm1.getValue()); to have the non-matching key/s printed.

It’s also a nice case for applying a stream operation if you like. If so, use the code from the answer by Oboe.

The code assumes that the keys are the same in both maps. You should probably check this assumption and issue a message if it doesn’t hold.

Upvotes: 1

Oboe
Oboe

Reputation: 2723

Try these:

map1.entrySet().stream()
            .filter(entry -> map2.get(entry.getKey()) != null)
            .filter(entry -> !map2.get(entry.getKey()).equals(entry.getValue()))
            .map(Map.Entry::getKey)
            .collect(Collectors.toList());

Upvotes: 1

Egor
Egor

Reputation: 40218

Here's what you can do:

  1. Iterate over the keys of both of your maps and collect them into a Set.
  2. For each entry in that Set, query values from both maps.
  3. Compare the values. Make sure your code handles cases when there's no value in one of the maps for the given key. Whether to consider that a mismatch, or an exceptional condition, is up to you.

Upvotes: 1

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