Added Stock Generation to Store.java

No Daniel. The logic behind the choice of a LinkedList was that the
LinkedList implementation of the List interface allows rapid resizing of
the element storage structure. This means that you can add or remove
items without having to worry about resizing the list, which becomes
very costly at large List sizes in an Array-backed List.

Also List<Item> list = new ArrayList<>(); is diamond notation, which was
introduced in Java 7. It is not, by any means, wrong.
Tinkered with Store.java

Basically, I fixed my mistakes.

Daniel. The idea is that you should not be equipping items in a slot
that's already full. Rather, you should first unequip the item, return
it to the player's Inventory, and then remove the equipping item from
the Inventory and equip it. At no point should any equipped item also be
in the character's Inventory, nor should any errant Items ever fall into
the Characters hands. That decision complicates some areas, and
simplifies others.