public class Stack<Item> {
	
	private Node first ;
	
	private class Node
	{
		private Node next ;
		private Item data ;
	}
	
	public boolean isEmpty()
	{
		return (first == null) ;
	}
	
	public void push(Item newData)
	{
		Node oldfirst = first ;
		first = new Node() ;
		first.data = newData ;
		first.next = oldfirst ;
	}
	
	public Item pop()
	{
		Item returnVal = first.data ;
		first = first.next ;
		return returnVal ;
	}
	
	public static void main( String args[]) 
	{
		Stack<String> s = new Stack<String>() ;
		s.push("my") ;
		s.push("dog") ;
		s.push("is") ;
		s.push("old") ;
		
		while (!s.isEmpty() ) 
		{
			System.out.println( s.pop() ) ;
		}
		
		Stack<Person> ps= new Stack<Person>() ;
		Person p1 = new Person(17,"Bob") ;
		ps.push(p1) ;
		p1 = new Person(18,"Sue") ;
		ps.push(p1) ;
		
		while (!ps.isEmpty() )
		{
			p1 = ps.pop();
			p1.Print();
		}
		
	}

}