1

package One;

/**
 * Created by Daniel on 4/6/2016.
 */

public class ArrayStack
{
    private static final int SIZE = 10; //size of array
    private Object[] item; //items within the stack
    private int numItem; //#of items

    public ArrayStack()
    {
        item = new Object[SIZE];
        numItem = 0;

    }

    // Pushes (adds)
    public void push(Object x)
    {

        if(item.length-1 == numItem)
        {
            item[numItem] = x;
            numItem--;

        }

    }

    //Pops (removes)
    public Object pop()
    {

        if(numItem == item.length-1)
        {
            item[numItem] = null;
            numItem--;
        }

        return item[numItem];

    }

}



---------------

2



package Two;

/**
 * Created by Daniel on 4/6/2016.
 */

public class LinkedStack
{
    private static class Node
    {
        int item;
        Node next;
    }

    private Node top = null; //node that is at the top of the stack is null

    public void push(int n)
    {
        Node newTop; //holds new top stack node
        newTop = new Node();
        newTop.item = n;
        newTop.next = top; //new node refers to old top
        top = newTop; //new top
    }

    public int pop()
    {
        int topItem = top.item;
        top = top.next; //popped item
        return topItem; //previous node is now the top

    }

}