package lists;

public class Stack implements ADTStack
{
    private Node top = null;
    private int size = 0;
    
    public Stack()
    {
        top = null;
        size = 0;
    }
    
    public boolean isEmpty()
    {
        return (top == null);
    }
    
    public boolean isFull()
    {
        return false;
    }
    
    public int getSize()
    {
        return size;
    }
    
    public void push(Object obj)
    {
        Node p = new Node(obj);
        p.setNext(top);
        top = p;
        size++;
    }
    
    public Object pop()
    {
        Object obj = top.getData();
        top = top.getNext();
        size--;
        return obj;
    }
    
    public Object peek()
    {
        return top.getData();
    }
}