不明白为什么我的方法不起作用？

Question

public class BlackJackRules
{
    Random generator = new Random();
    int c = 0;
    String card1;

    /* Creates a random number which turns into
     * a string card(card1). 
     */

    public String getCard()
    {
        c = generator.nextInt()+14;
        if(c == 1)
            card1 = "Ace";
        else if(c == 2)
            card1 = "Two";
        else if(c == 3)
            card1 = "Three";
        else if(c == 4)
            card1 = "Four";
        else if(c == 5)
            card1 = "Five";
        else if(c == 6)
            card1 = "Six";
        else if(c == 7)
            card1 = "Seven";
        else if(c == 8)
            card1 = "Eight";
        else if(c == 9)
            card1 = "Nine";
        else if(c == 10)
            card1 = "Ten";
        else if(c == 11)
            card1 = "Jack";
        else if(c == 12)
            card1 = "Queen";
        else if(c == 13)
            card1 = "King";
        return card1;
    }
}

and here is the driver program....

public class BlackJack
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        String userStart = new String();
        String userQuit = new String();
        String card1 = new String();

        System.out.println("Would you like to play some BlackJack?");
        userStart = scan.next();
        if(userStart.equalsIgnoreCase("yes"))
        {
            System.out.println("Here we go...");
            while(userQuit.equalsIgnoreCase("yes"))
            {
                System.out.println("Your first card is a " + card1.getCard());
            }
        }
        else
            System.out.println("Okay.");
        }
    } 
}   

I just can't figure it out... I have tried rearranging my code. I am fairly new taking an AP course in high-school and am struggling with the concepts of methods. Thanks for your help!

Answer 1

You haven't created an instance of BlackJackRules

This

String card1 = new String(); 

Should be

BlackJackRules card1 = new BlackJackRules();

Then this will work

System.out.println("Your first card is a " + card1.getCard());

Since getCard() is in the BlackJackRules class, you first need to create an instance of it to use its method

Also in your method, you want to just use this

c = generator.nextInt(13) + 1

Answer 2

Instead of

c = generator.nextInt()+14;

You probably want.

c = generator.nextInt(13) +1;

The code as written will most likely not produce the desired result even if it compiles and runs, since you will be generating integers in the full range of a 32-bit integer.

Answer 3

In addition to the previous answers:

• Your BlackJackRules class seems to have an extra set of curly braces. Not sure if this is particularly important but it made Eclipse complain anyway.
• The while loop inside your main method will not run. userQuit hasn't been given a value so your equalsIgnoreCase will fail and the program will end.

On the second point, it'd probably be best to change that loop to a do-while and add a prompt asking if the user wishes to draw another card.