Question

How can I print an amount of random vehicle in vec? For instance if the n is 2, then print bus = 16.

class T {

    Map<String, Integer> vec = new HashMap<String, Integer>();
    List<String> transp = Arrays.asList("Car", "Bus", "Train");
    List<Integer> amount = Arrays.asList(58, 16, 33);

    int val() {
        for (int i = 0; i < vec.size(); i++)
            vec.put(transp.get(i), amount.get(i));
        System.out.println(vec);
        Random rand = new Random();
        int n = 0 + rand.nextInt(vec.size());
    }
}

Thanks!

Answer 1

Given that you’ve already got the key/value pairs as separate lists, why not just use:

String randomVehicle = transp.get(n);
int randomAmount = amount.get(n);

If you have to do it via the map, you could use:

Iterator<Map.Entry<String, Integer>> iterator = vec.entrySet().iterator();
Map.Entry<String, Integer>> entry = iterator.next();
for (int i = 0; i < n; i++)
{
    entry = iterator.next();
}
String randomVehicle = entry.getKey();
Integer randomAmount = entry.getValue();

It’s not really a good way of doing things – maps are meant for looking things up by key, not for getting entries by index, given that they’re inherently unordered.