[Testdome] train composition

we use a deque to act as a doubly linked list as both stack and queue

there is actually deque in java too that can be implemented as a linkedlist like this

import java.util.Deque;
import java.util.LinkedList;
public class TrainComposition {
    private Deque<Integer> deque;

    public TrainComposition() {
        deque = new LinkedList<>();
    }

    public void attachWagonFromLeft(int wagonId) {
        deque.addFirst(wagonId);
    }

    public void attachWagonFromRight(int wagonId) {
        deque.addLast(wagonId);
    }

    public int detachWagonFromLeft() {
        if (!deque.isEmpty()) {
            return deque.removeFirst();
        } else {
            throw new IllegalStateException("Train composition is empty");
        }
    }

    public int detachWagonFromRight() {
        if (!deque.isEmpty()) {
            return deque.removeLast();
        } else {
            throw new IllegalStateException("Train composition is empty");
        }
    }