Urn Source Code 2

Urn Class, source code file Urn1.cs

/// <summary>
/// Simulate drawing balls from an urn (jar) without replacement.
/// Use an ArrayList collection to keep track of the balls.
/// </summary>

public class Urn
{
    // Private instance variables.
    private ArrayList balls;
    private int _totalBalls;
    private Random r = new Random();

// Parameterized constructor.
    public Urn(int initialNumBalls)
    {
        // _totalBalls must be nonnegative.
        if (initialNumBalls > 0)
        {
            _totalBalls = initialNumBalls;
        }
        else
        {
            _totalBalls = 0;
        }

// Initialize collection of balls.
        balls = new ArrayList();
        for (int i = 1; i <= _totalBalls; i++)
        {
            balls.Add(i);
        }
    }

// Public read-only method.
    public int TotalBalls
    {
        get { return _totalBalls; }
    }

// Public methods:

// Return number of balls remaining.
    public int BallsRemaining()
    {
        return balls.Count;
    }

// Return true count of balls is zero.
    public bool IsEmpty
    {
        get { return balls.Count == 0; }
    }

// Draw a ball from urn.
    public int Draw()
    {
        int n = r.Next(0, balls.Count);
        int ball = (int) balls[n];
        balls.RemoveAt(n);
        return ball;
    }

// Print remaining balls in urn.
    public override string ToString()
    {
        string s = "";
        foreach (int i in balls)
        {
            s += i.ToString() + " ";
        }
        return s;
    }
}