//java doesn't allow generic array

//avoid casting, it shows weakness

//generic implementation

//handling multiple type of data

// maintain pointer to first node and remove/add from front.

// Stack<Integer> stack = new Stack<Integer>();

public class Stack<Item> {

private Node first=null;//inner class variables as stack ?? check

// for queues use another variable too , last

// public LinkedStackOfStrings(){

// Node n=new Node();

// System.out.println(n.item+"--");

// }

//inner class

//should not have static members

//inner class has extra overhead of 8 bytes

private class Node{

//access modifier doesn't matter

Item item;//instance variables have a default value

Node next; //object , a reference to another node

// public String toString(){

// return item ;

// }

}

public boolean isEmpty(){

return first==null;

}

public void push(Item item){

Node oldfirst=first;

// System.out.println(first);

first=new Node();//object 16 bytes overhead

first.item=item;// 8 bytes reference to string

first.next=oldfirst;// 8 bytes reference to node (so 40 bytes per stack node)

System.out.println(first.item);

System.out.println(first.next);

// System.out.println(first + "===========");

}

public Item pop(){

Item item=first.item;

first=first.next;// first node is deleted is reclaimed by the garbage collector

return item;

}

public static void main(String[] args ){

Stack l=new Stack();

// System.out.println(l.first);

// System.out.println("====");

String s="hello";

l.push(s);

String sa="hello2";

l.push(sa);

String sab="hello3";

l.push(sab);

}

}