Slot machine simulation

static String[] reels = { "Cherries", "Oranges", "Plums", "Bells", "Melons", "Bars" };
static int numberOfReels = 3;

char playAgain;
double amountBet = 0;
double totalWon = 0;
DecimalFormat dollar = new DecimalFormat("#,##0.00");


// Create a Scanner object for keyboard input.
Scanner keyboard = new Scanner(System.in);

/**
 * Method should return the number of times an occurrence of a reel
 *
 * @param reels
 * @return
 */
static int determinePayOutPercentage(List<String> reels) {

    Multiset<String> reelCount = HashMultiset.create();
    reelCount.addAll(reels);

    // order the number of elements by the higest
    ImmutableMultiset<String> highestCountFirst = Multisets.copyHighestCountFirst(reelCount);

    int count = 0;
    for (Entry<String> entry : highestCountFirst.entrySet()) {
        count = entry.getCount();
        break;
    }
    return count;
}

/**
 * Method should get a reel randomly
 *
 * @return string representing reel
 */
static String getRandomReel() {

    // Create a Random object, set seed to the number of elements in array
    Random randomNumber = new Random();
    return getReel(randomNumber.nextInt(reels.length));
}

/**
 * Method should return reel based on index of array 0 - cherries 1 -
 * oranges 2 - plums 3 - bells 4 - melons 5 - bars
 *
 * @param element
 * @throws IndexOutOfBoundsException
 *             if {@code index} is negative or is not less than 6
 * @return reel
 */
static String getReel(int index) {

    checkElementIndex(index, reels.length);

    return reels[index];

}

// Play the slot machine once, and repeat the game as long
// as the user confirms they want to continue to play.
do {
    System.out.println("Welcome to the Slot Machine Simulation.");

    // Get the amount the user wants to bet.
    System.out.print("\nEnter the amount you would like to bet: $");
    amountBet = keyboard.nextDouble();

    // Skip a line.
    System.out.println();

    // generate random reels
    List<String> reels = Lists.newArrayList();
    for (int x = 0; x < numberOfReels; x++) {
        reels.add(getRandomReel());
    }

    // display reels
    System.out.println(Joiner.on("--").join(reels));

    // determine the payout percentage
    int payoutPercentage = determinePayOutPercentage(reels);

    // calcuate the amount won
    double amountWon = payoutPercentage * amountBet;

    // keep running total of amount won
    totalWon += amountWon;

    // Display the amount won.
    System.out.println("\nYou win $" + dollar.format(amountWon));

    // Prompt the user to play again.
    System.out.println("\nWould you like to play again?");
    System.out.print("Enter Y for yes or N for no: ");
    String input = keyboard.next(); // Read a string.
    playAgain = input.charAt(0); // Get the first character.

} while (playAgain == 'Y' || playAgain == 'y');

System.out.println("You won a total of $" + dollar.format(totalWon));

Welcome to the Slot Machine Simulation.

Enter the amount you would like to bet: $250

Bells--Bells--Bars

You win $500.00

Would you like to play again?
Enter Y for yes or N for no: y
Welcome to the Slot Machine Simulation.

Enter the amount you would like to bet: $500

Bells--Bells--Cherries

You win $1,000.00

Would you like to play again?
Enter Y for yes or N for no: n
You won a total of $1,500.00

@Test(expected=IndexOutOfBoundsException.class)
public void get_reel_negative () {
    SlotMachineSimulation.getReel(-1);
}

@Test(expected=IndexOutOfBoundsException.class)
public void get_reel_greater_than_6 () {
    SlotMachineSimulation.getReel(-1);
}


@Test
public void get_reel_cherries () {
    assertEquals("Cherries", SlotMachineSimulation.getReel(0));
}

@Test
public void get_random_reel () {
    assertNotNull(SlotMachineSimulation.getRandomReel());
}

@Test
public void determine_pay_out_percentage_two () {

    List<String> randomStrings = Lists.newArrayList("one", "one", "two", "three");

    assertEquals(2, SlotMachineSimulation.determinePayOutPercentage(randomStrings));;
}

@Test
public void determine_pay_out_percentage_one () {

    List<String> randomStrings = Lists.newArrayList("one", "two", "three");

    assertEquals(1, SlotMachineSimulation.determinePayOutPercentage(randomStrings));;
}

@Test
public void determine_pay_out_percentage_zero () {

    List<String> randomStrings = Lists.newArrayList();

    assertEquals(0, SlotMachineSimulation.determinePayOutPercentage(randomStrings));;
}