Stack implementation using linked list

Stack impl

public class Stack<T> { 
    private static class Node<T> {
        private T data;
        private Node<T> next;
        
        public Node(T data) {
            this.data = data;
        }
    }
    
    private Node<T> top;
    
    public T pop() {
        if (top == null) {
            return null;
        }
        
        T item = top.data;
        top = top.next;
        return item;
    }
    
    public void push(T data) {
        Node<T> newTop = new Node<>(item);
        newTop.next = top;
        top = newTop;
    }
    
    public T peek() {
        if (top == null) {
            return null;
        }
        
        return top.data;
    }
    
    public boolean isEmpty() {
       return top == null;
    }
}