Solitaire class

import java.util.ArrayList;
/**
 * Solitaire
 * Defines and creates objects of the solitaire class using array lists.
 * @Cody Young
 * @October 27, 2016
 */
public class Solitaire
{
    //Instance variable for piles array list
    private ArrayList<Integer> piles = new ArrayList<>();

    /**
     * Constructor method for Solitaire class objects. Initializes card piles to random sizes.
     */
    public Solitaire()
    {
       int piles_total = 0; //Variable that tracks running total number of cards across piles

       while (piles_total < 45)
       {
           //Generate random number, subtract max
           int rand_number = (int) (Math.random () * (45 - piles_total)) + 1;
           piles.add(rand_number);
           piles_total += rand_number;  //Add # of cards in each pile to total - must equal 45
       }
    }

    /**
     * Method returning true if solitaire game is over, false by default.
     */
    public Boolean over()
    {
        for(int i = 1; i < 10; i++)
        {
           if (piles.indexOf(i) == -1) //Checks if value at index is 1-9; if not, continues
           {
               return false;
           }
        }
        return true;        //If no values return -1, game is over
    }

    /**
     * Method that draws one card from each pile and adds to a new pile.
     * Each iteration represents one round.
     */
    public void round()
    {
      int newpile_total = 0;        //Running total of cards taken from piles

      for (int i = 0; i < piles.size(); i++)
        {
           int pile_sub = piles.get(i) - 1;     //Variable for pile subtraction
           piles.set(i, pile_sub);              //Gets pile value, subtracts one and places back into pile
           if (piles.get(i) == 0)
            {
               piles.remove(i);      //If value at index i = 0, remove pile
               i--;                  //Decrement i after removing piles
            }
           newpile_total += 1;       //Tracks how many cards are subtracted, adds to total
        }
        piles.add(newpile_total);    //Adds total cards pulled from piles, appends list
    }

    /**
     * Returns a string representation of a Solitaire object.
     */
    public String toString()
    {
        return piles.toString();
    }
}