return n'th value and key from a hash map in java

Question

For my schooling I have to write a programm, which read and return costumer value from data. To do that, I have created an double hash map. In the inner, i have mapped for example, keys like name, to values like chris. The outer map is for mapping the inner maps, to the costumers name.

To create a list of the accessible files/costumers, I have created that code:

for (HashMap<String, String> file: output.MapForFileMaps.values())
    {
        h = h + 1;
        if (fileRequest == h)
        {
            requestIsListet = true;
            for (String key: file.keySet())
            {
                p = p + 1;
                System.out.println("Press " + p + " for " + key);
            }
        }
    }

Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?

Current Problem is, that I want to check wheather the input is connected to a accessible part of the map, or not. So I could return this area of code by an while loop, while request is not available.

There is no guarantee the nth value is going to be the same over multiple iterations for a HashMap. See: https://stackoverflow.com/questions/2144776/is-the-order-of-values-retrieved-from-a-hashmap-the-insertion-order — Compass, Nov 20 '18 at 14:37
It seems you're using wrong data structure for the problem because, by definition, there is no Nth key/value in hash map. — TheJavaGuy-Ivan Milosavljević, Nov 20 '18 at 14:38
What’s wrong with designing a proper `Customer` class with instance variables (fields) for name, etc.? In case it helps you. a `LinkedHashMap` maintains insertion order, so you may use its iterator to count to the *n*th inserted item (provided that no item has later been removed again). — Ole V.V., Nov 20 '18 at 15:09

score 1 · Answer 1 · answered Nov 20 '18 at 14:37

Question: Could I reach directly that part of the hash map, which is needed, by asking for the value or key of the hash map on the n`th place?

Answer: You COULD, but it wouldnt be efficcient, Hashmaps store elements based on a hash of the key, so the first inserted element isnt per definition on index 0. You can instead use the key to get the value

Take a look here: https://www.geeksforgeeks.org/internal-working-of-hashmap-java/

return n'th value and key from a hash map in java

1 Answers1