Method push

src/main/java/edu/princeton/cs/algs4/Stack.java:91–97

Adds the item to this stack. @param item the item to add

(Item item)

     * @param  item the item to add
     */
    public void push(Item item) {
        Node<Item> oldfirst = first;
        first = new Node<Item>();
        first.item = item;
        first.next = oldfirst;
        n++;
    }

    /**
     * Removes and returns the item most recently added to this stack.