import java.util.Random;  // Warn Java we want to use Random

/**
 * The Die class models a die of the sort you'd roll:  It
 * can be created with as many sides as you wish, and has
 * a roll method that returns an appropriate random result.
 */

public class Die
{
    // numSides CANNOT be made static without changing the behavior of the
    // class. We need to be able to have different numbers of sides for each
    // Die, so each needs its own copy of numSide.
    private int numSides;   
    // rng COULD be static -- the program would still work correctly, But SHOULD
    // it be? We'd save some memory by only keeping one copy of Random.
    private static Random rng = new Random(); 
    // It makes sense to make all constants static -- it would have the same value
    // across Die instances anyway.
    private static final int MAX_NUM_SIDES = 20; 
    private static int numDice = 0;  // HAS to be static for program to work properly
    
    /**
     * Constructor for objects of class Die.  The default constructor
     * (this one, since it takes no parameters) will create a six-sided
     * die.
     */
    public Die()
    {
        numSides = 6;
        numDice = numDice + 1;
    }
    
    /**
     * This constructor creates a Die object with the specified number
     * of sides.
     */
    public Die(int sides)
    {
        if (sides > MAX_NUM_SIDES) {
            System.out.println("That's ridiculous.  I'm using 6 instead");
            numSides = 6;
        }
        else {
            numSides = sides;
        }
        numDice = numDice + 1;
    }

    /**
     * Simulates a roll of this Die instance.  Picks a 
     * random value in the appropriate range and returns it.
     */
    public int roll()
    {
        int rollValue = rng.nextInt(numSides);
        return rollValue+1;
    }
    
    /**
     * Returns number of sides. Cannot be a static method since it
     * references a field that's not static.
     */
    public int getNumSides()
    {
        return numSides;
    }
    
    /**
     * This method CAN be static, since it only accesses static fields. In
     * general, if a method CAN be static, it probably SHOULD be.
     */
    public static int getNumDice() 
    {
        return numDice;
    }
    
}