Question

I know that ArrayList provide ability to get item at position get(position), and LinkedHashTable provide sorting, but it not able to get item at position. So, question: is any generic collection in java with features:

• sorting

• get by position

• provide Key/Value generic type.

Please, give me code example of listed features, if required generic exists.

Answer 1

I apologize for over complicating things earlier!

Use a TreeMap. When you want to

get(position)

just do the following:

K key = treemap.getKeys().get(position)
V value = treemap.get(key);

==========================

My old over complex incorrect answer from before:

You can use an ArrayList<Pair<K implements Comparable,V>> where you implement comparable on the Pair<K,V> and K has Comparable implemented. Then you can use Collections.sort(List<Pair<K,V>) on the Arraylist.

Then you would maintain a HashMap<K,V> so that you can retrieve elements by K. That means you will have to remember to update both data structures. That means O(N) to add an element 🙁 . Also, to simplify the logic, you would wrap the HashMap and ArrayList in an object.

public class Pair<K extends  Comparable<K>, V> implements Comparable {

    private final K first;

    private final V second;

    public Pair(K first, V second) {
        this.first = first;
        this.second = second;
    }

    public K getFirst() {
        return first;
    }

    public V getSecond() {
        return second;
    }

    public int compareTo(K other) ; // TODO
}