// gets you access to System.out
import java.io.*;
// gets you access to the LinkedList class
import java.util.*;

public class Stack2{
      
	// where we'll store the data.
 	// notice we don't need a count anymore
    	// since the linked list will grow and shrink as we
	// add or delete things.
	private LinkedList data;

	// the constructor
	public Stack2(){
		data = new LinkedList();	 
	}

	public void push(int thing){
		data.add(new Integer(thing));
		// since LinkedLists can only store objects(see API docs)
		// we have to wrap the primitive type in an object reference.
		// we'll cover this in the next lecture.
	}

	public int pop(){
		// get the information back from the LinkedList.
		// the LinkedList is 0 based but the size method
		// returns us the count of items and that is why
		// we have to subtract one.
		Integer retVal = (Integer)data.remove(data.size()-1);

		// return the user the data of type int
		return retVal.intValue();
	}

	// the code that gets run when you type "java Stack2".
	public static void main (String[] args){
		Stack2 s = new Stack2();

		s.push(1);
		s.push(2);
		s.push(3);
		System.out.println(s.pop());
		System.out.println(s.pop());
	}

}