Stack using a linked list

Stack.java

public class Stack<E> {

    private class Node<V> {
        private V data;
        private Node<V> next;

        Node(V data) {
            this.data = data;
        }
    }

    private Node<E> top;

    // Time: O(1)
    // Space: O(1)
    public E push(E item) {
        Node<E> node = new Node<>(item);
        node.next = top;
        top = node;

        return item;
    }

    // Time: O(1)
    // Space: O(1)
    public E pop() {
        if (top != null) {
            Node<E> popped = top;
            top = top.next;

            return popped.data;
        }

        return null;
    }

    // Time: O(1)
    // Space: O(1)
    public boolean isEmpty() {
        return top == null;
    }

    // Time: O(1)
    // Space: O(1)
    public E peek() {
        return top != null ? top.data : null;
    }

    public static void main(String[] args) {
        Stack<String> stack = new Stack<>();

        for (int i = 0; i < 10; i++) {
            stack.push("Item " + i);
        }

        System.out.println("Empty stack: " + stack.isEmpty());
        System.out.println("Peek: " + stack.peek());

        for (int i = 0; i < 10; i++) {
            System.out.println(stack.pop());
        }

        System.out.println("Empty stack: " + stack.isEmpty());
    }

}