package howto;

import java.awt.*;

public class Stack extends Panel
{
   private TextField [] _rgtf = new TextField [5];

   private static final int DELTA = 5;

   private double [] _rgd = new double [DELTA];

   private int _n = -1;

   public Stack()
   {
      setLayout(new GridLayout(0, 1, 5, 5));

      for (int i = 0; i < _rgtf.length; i++)
      {
         _rgtf[i] = new TextField();

         _rgtf[i].setEditable(false);

         add(_rgtf[i]);
      }
   }

   public void display()
   {
      for (int i = _n; _n - i < _rgtf.length; i--)
      {
         if (i > -1)
            _rgtf[_n - i].setText(String.valueOf(_rgd[i]));
         else
            _rgtf[_n - i].setText("");
      }
   }

   public void push(double d) throws StackException
   {
      if (_n + 1 > _rgd.length - 1)
      {
         double [] rgd = new double [_rgd.length + DELTA];

         System.arraycopy(_rgd, 0, rgd, 0, _rgd.length);

         _rgd = rgd;
      }

      _rgd[++_n] = d;
   }

   public double pop() throws StackException
   {
      if (_n < 0)
      {
         throw new StackException("stack empty");
      }

      return _rgd[_n--];
   }

   public int count()
   {
      return _n + 1;
   }
}