Please modify this Stack class. Then, construct a Calculator app which implements Reverse Polish Notation using the newly modified Stack class. in java

public class Stack { private class Node { private T item; private Node next;

public Node( ) { item = null; next = null; }

public Node(T newItem, Node newNext) { item = newItem; next = newNext; } } //End of Node inner class

private Node head; int size;

// Create an empty stack. public Stack() { }

// This method pushes an item onto the stack. public void push(T itemName) { }

// This method pops the top item from the stack and // also returns the value of the popped item. public T pop() { }

// This method returns the "top" item in the stack // without popping it. public T top() { }

// Returns number of elements in the stack. public int size() { } // Is the stack empty? public boolean isEmpty() { }

// Make the stack empty. public void makeEmpty() { }

}