import java.util.Vector;

/**
 * RationalStack provides a stack collection of Rational objects
 */
public class RationalStack
{
    private Vector<Rational> _data = new Vector<Rational>();

    /**
     * pop will remove and return the Rational object from the top of the stack
     * @return the Rational at the top of the stack
     */
    public Rational pop()
    {
        int sz = _data.size();
        if (sz > 0)
        {
            Rational r = _data.remove(sz-1);
            return r;
        }
        return null;
    }

    /**
     * push will add a new Rational object to the top of the stack
     * @param value the Rational object to add to the stack
     */
    public void push(Rational value)
    {
        _data.add(value);
    }

    /**
     * isEmpty will return true if there are no Rational elements on the stack
     * @return true if there are no Rational elements on the stack
     */
    public boolean isEmpty()
    {
        return _data.isEmpty();
    }

    /**
     * clear will remove all Rational objects from the stack
     */
    public void clear()
    {
        _data.clear();
    }

    /**
     * size returns the number of Rational objects in the stack
     * @return the number of Rational objects in the stack
     */
    public int size()
    {
        return _data.size();
    }
}