package stackqueue;

import java.util.ArrayList;

public class Stack
{
    private ArrayList array;

    public Stack()
    {
        array = new ArrayList();
    }

    public void push(Object item)
    {
        array.add(0, item);
    }

    public void pop()
    {
        if (array.size() > 0)
            array.remove(0);
    }

    public Object peek()
    {
        if (array.size() > 0)
            return array.get(0);
        else
            return null;
    }

    public String toString()
    {
        return array.toString();
    }

    public boolean isEmpty()
    {
        return array.size() == 0;
    }
}