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Thread: Help with Card Game

  1. #1
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    Default Help with Card Game

    Hi guys,

    this is my first time posting here so please go easy on me. So I'm trying to assign a suit, number, and value for the cards for a Black Jack game for my Computer Programming class but I'm running into a problem. I have variables in my "Card.class" for all value, number, and suit but it just doesn't seem to work. It compiles fine but when I run the applet, I get an error saying something along the lines of: NullPointerException at line 64. Which is the line, "Cards[i].suit = "Spade";" . I'll appreciate any help.




    // Import section
    // Use this section to add additional libaries for use in your program.
    import java.applet.*;
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    import java.lang.Math;
     
     
     
    // This begins the class definition.
    // Notice that this is a "world".  You can tell since it extends Applet.
    public class BlackJack extends Applet implements Runnable, /*KeyListener,*/ MouseMotionListener, MouseListener
     
    {
    	//variable declaration section
    	// public  datatype  variablename
     
    	public int xTitle;
    	public int yTitle;
    	public Card[] Cards;
    	public int sizeC;
    	public int randomXpos, randomYpos, randomCard;
    	public Image cardDeck;
     
     
     
     
     
    	Graphics bufferGraphics;
    	Image offscreen;
     
     
    	//Sets up a Thread called thread
    	Thread thread;
     
    	// Method definition section
     
    	// init() is the first method an Applet runs when started
    	public void init()
    	{
    		//Initialize variables
    		xTitle=250;
    		yTitle=50;
    		sizeC = 52;
     
    		Cards = new Card[sizeC];
    		/*for(int j = 0; j<13; j++)
    		{
    			for(int i = j; i<52; i = i+13)
    			{
    				Cards[i].value = j+1;
    				Cards[i].number = j+1;
    			}
    		}*/
     
    		for(int i = 0; i < 13; i++)
    		{
    			Cards[i].suit = "Spade";
    		}
    		for(int i = 13; i < 26; i++)
    		{
    			Cards[i].suit = "Club";
    		}
    		for(int i = 26; i < 39; i++)
    		{
    			Cards[i].suit = "Diamond";
    		}
    		for(int i = 39; i < 52; i++)
    		{
    			Cards[i].suit = "Heart";
    		}
     
    		cardDeck = getImage(getDocumentBase(), "CardDeck.gif");
     
     
     
    		//double buffering
    		offscreen = createImage(800,600); //create a new image that's the size of the applet
    		bufferGraphics = offscreen.getGraphics(); //set bufferGraphics to the graphics of the offscreen image.
     
    		setSize(800, 600);
     
    		addMouseListener(this);
    		addMouseMotionListener(this);
    		//Set up the thread
    		thread = new Thread(this);  //constructs a new thread
    		thread.start();				//starts the thread
    	}//init()
    Last edited by JSeol14; April 21st, 2012 at 10:38 PM.


  2. #2
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    Default Re: Help with Card Game

    Here's an idea, though I don't have the Card.java code.

    for(int i = 0; i < 13; i++)
    		{
                             try{
     
    			Cards[i].suit = "Spade";
    }
     
     
    catch(NullPointerException npe)
    {
    System.out.println("Card " + i  + " is null!");
    }
    		}
    That would detect where it's going Null. However, I think I see the problem.

    However, it would seem to me that the problem is that you define a Card array but never initialize it with something like
    for (int i =0; i < Cards.length; i++)
    {
    Cards[i]= new Card();
    }

    If it's not initalized, then the entire Card there is null, hence you can't go referring to .value and stuff of a null Card.

  3. The Following User Says Thank You to javapenguin For This Useful Post:

    JSeol14 (April 21st, 2012)

  4. #3
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    Default Re: Help with Card Game

    Wow thank you so much. I can't believe I overlooked that so easily. I feel pretty stupid now. But thank you again!

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