How can I foreach a hashmap?

Question

I have a hashmap with the values :

1 - 18;
1 - 19;
1 - 20;
3 - 21;
3 - 22;
8 - 23;
8 -24;
8 - 25;
11 - 26;

And I gotta loop it and check whether the key is equal the specific value, which will be a parameter. So, let's say my parameter is the number 3. It should return this to me:

21, 22.

Thanks!

What you have mentioned is not an HashMap. HashMap cannot have duplicate keys. — shruti1810, May 22 '15 at 17:54
Should I use an arraylist or what then, to store multiple keys (ID) and value? — Henry Stuart, May 22 '15 at 17:54
possible duplicate of [HashMap with multiple values under the same key](http://stackoverflow.com/questions/4956844/hashmap-with-multiple-values-under-the-same-key) — kiranpradeep, May 22 '15 at 18:00
I'm not sure how I could adapt the duplicated question to my issue :( — Henry Stuart, May 22 '15 at 18:05

Bojan Kseneman · Accepted Answer · 2015-05-22T19:44:17.167

Map<Integer, Integer> map = ...;

for (Integer key : map.keySet()) {
    // do something
}

Or

Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry<Integer, Integer> entry = entries.next();
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

EDIT: According to your comment this is what you need, just paste this somewhere and observe and play with it a bit, I tryied to comment the imporant sutff

private void hashMapTest() {
    HashMap<Integer, List<Integer>> testMap = new HashMap<>();
    int i; // Iterator

    // ArrayLists that hold the integer values at specific key
    List<Integer> list1 = new ArrayList<>();
    List<Integer> list2 = new ArrayList<>();
    List<Integer> list3 = new ArrayList<>();
    List<Integer> list4 = new ArrayList<>();

    // Fill the lists with some demo data.
    for (i = 0; i < 5; ++i) {
        list1.add(i);
    }

    for (; i < 10; ++i) {
        list2.add(i);
    }

    for (; i < 15; ++i) {
        list3.add(i);
    }

    for (; i < 20; ++i) {
        list4.add(i);
    }

    // Add the data holders to the map. Note the keys in HashMap must be unique!!
    testMap.put(1, list1);
    testMap.put(2, list2);
    testMap.put(3, list3);
    testMap.put(4, list4);

    // Let's you want to get the values with the key 3 amd print it out
    for (Integer integer : testMap.get(3)) {
        Log.d("loop test", "Integer: " + integer);
    }

    // Now let's say you want to add some value to one of the lists, say key 2
    testMap.get(2).add(12314151);
    testMap.get(2).add(1231);
    testMap.get(2).add(77565);

    // And print it
    for (Integer integer : testMap.get(2)) {
        Log.d("loop test2", "Integer: " + integer);
    }

}

Will produce something like this

05-22 21:34:35.765  20092-20092/? D/loop test﹕ Integer: 10
05-22 21:34:35.765  20092-20092/? D/loop test﹕ Integer: 11
05-22 21:34:35.765  20092-20092/? D/loop test﹕ Integer: 12
05-22 21:34:35.766  20092-20092/? D/loop test﹕ Integer: 13
05-22 21:34:35.766  20092-20092/? D/loop test﹕ Integer: 14
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 5
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 6
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 7
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 8
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 9
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 12314151
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 1231
05-22 21:34:35.766  20092-20092/? D/loop test2﹕ Integer: 77565

Hello! THank you very much for your time, but this sample doesn't fix my problem, unfortunately. I need to pass a number via parameter and it should return me all values which are equal to that number — Henry Stuart, May 22 '15 at 18:01
Equal to key! For instance, my hashmap contains the following (key and value respectively) _3 - 5 3 - 6 1 - 7_ ~ so, if I ask for the value 3, it should return the 5 and 6. I should use a > map, right? But how could I add and retrieve the values? — Henry Stuart, May 22 '15 at 18:12
I will show you later if nobody else will do it sooner, got dinner. — Bojan Kseneman, May 22 '15 at 18:15
Yes, I'm making a simple example for you. You will copy paste it to your activity and all will be clear — Bojan Kseneman, May 22 '15 at 19:22

How can I foreach a hashmap?

1 Answers1