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Thread: NullPointerException error

  1. #1
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    Default NullPointerException error

    Hi, my program reads out of a textfile containing about 20 hockey players. At the beginning of the program, the user is given the option to sort by name, rating, club or position. No matter what I press, I always get a nullpointerexception error. This never happened before and the program works fine on my friends computer, it also used to work fine on mine and then I randomly got this error. What do I do to fix this?


    This is what is says in the bluej thingy



    java.lang.NullPointerException
    at java.lang.String$CaseInsensitiveComparator.compare (String.java:1217)
    at java.lang.String$CaseInsensitiveComparator.compare (String.java:1211)
    at java.lang.String.compareToIgnoreCase(String.java:1 258)
    at FINAL.sort(FINAL.java:206)
    at FINAL.options(FINAL.java:48)
    at FINAL.main(FINAL.java:41)


  2. #2
    Super Moderator copeg's Avatar
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    Default Re: NullPointerException error

    What do I do to fix this?
    Your first need to post code, preferably an abbreviated version, which clearly demonstrates the problem. The stack trace you posted provides a lot of information but is meaningless without the context of the code that throws the exception.

  3. #3
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    Default Re: NullPointerException error

    I get the error at this part of my program. It's weird though, it was working on my computer a few days ago and I suddenly got this error.


      if(options.equalsIgnoreCase("A"))
            {
                for (int x=0; x<players.length; ++x)
                {
                    for (int y=0;y<players.length-1; ++y)
                    {
                        if (players [y][0].compareToIgnoreCase(players [y+1][0]) > 0)  
                        {  
                            for(int b=0;b<=4;b++)
                            {
                                String temp = players [y][b];          
                                players [y][b] = players [y + 1][b];      
                                players [y + 1][b] = temp;
                            } 
                        }
                    }
                }
            }

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    Default Re: NullPointerException error

    Better, but the code still doesn't provide much context. An SSCCE is much more demonstrative. As is, I could guess that not all of your players array has been instantiated.

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    Default Re: NullPointerException error

    Thanks, it works now. i have another question, when I add a player to the database, it works fine. But when I try to remove a player from the database, it doesn't work. Another thing is, after I use the remove function, the other functions won't work anymore (for example, after using remove, i tried to sort the players by name, it didn't work because I got an array out of bounds error) Here is the code I use for adding players



    public static void add(String players [][],String args[]) throws IOException
        {   
            BufferedReader c = new BufferedReader(new InputStreamReader(System.in));
     
            PrintWriter output = new PrintWriter ( new FileWriter ("nhlstats.txt",true));//append file
     
            System.out.println ("Enter the name of the player (first then last)");
            String hplayer = c.readLine ();
     
            System.out.println ("Enter the position(C,RW,LW,D,G) of " + hplayer);
            String posadd = c.readLine ();
     
            System.out.println ("Enter the rating of " +hplayer);
            String ratingadd=c.readLine ();
     
            System.out.println ("Enter the country of origin of " + hplayer);
            String countadd = c.readLine ();
     
            System.out.println ("Enter the current team " + hplayer + " plays for");
            String clubadd = c.readLine ();
     
            System.out.println ("");
            System.out.println ("");
            System.out.println("The player has been added toe.");
            System.out.println("Please see text file for the added players.");
     
            int x = 0;    
            for (int i = 0 ; i <=players[x].length-1 ; ++i)
            {
                if (players [x][0] == null)
                {
                    i = x;
                    break;
                }
            }
            players [x][0] = hplayer;
            players [x][1] = posadd;
            players [x][2] = ratingadd;
            players [x][3] = countadd;
            players [x][4] = clubadd;
            output.println ();
            output.println (hplayer);
            output.println (posadd);
            output.println (ratingadd);
            output.println (countadd);
            output.println (clubadd);
            output.close();
            for (int j=0; j<players.length; ++j)//sort the name after it is added
                {
                    for (int y=0;y<players.length-1; ++y)
                    {
                        if (players [y][0].compareToIgnoreCase(players [y+1][0]) > 0)  
                        {  
                            for(int b=0;b<=4;b++)
                            {
                                String temp = players [y][b];          
                                players [y][b] = players [y + 1][b];      
                                players [y + 1][b] = temp;
                            } 
                        }
                    }
                }
        }


    The code I "tried" to use for removing players from the database is:

    public static void takeout(String players[][],String args[]) throws IOException
        {
            BufferedReader c = new BufferedReader (new InputStreamReader (System.in));
            PrintWriter out = new PrintWriter ( new FileWriter ("nhlstats.txt"));
            System.out.println ("What do you want to remove?.");
            String read = c.readLine ();
            for (int x =0; x<=players.length-1; ++x)
            {   
     
                if (players[x][0] != null)     
                {
     
                    if (players[x][0].equalsIgnoreCase(read))     
                    {
                        for (int y = 0; y <= 4; ++y)
                        {
                            players [x][y] = null;
                        }
                    }
     
     
                }
            }
     
            for (int x =0; x<=players.length-1; ++x)
            {   
                for (int y = 0; y <= 4; ++y)
                {
                    if (players[x][y] != null)
                    {
                        out.println(players[x][y]);
                    }
                }
                out.close();
            }
        }


    I think what happens is that instead of that specific player getting deleted from the text file, all the players get deleted. How do I delete only one player?
    Last edited by blazerix; January 23rd, 2011 at 04:13 PM.

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    Default Re: NullPointerException error

    I really don't mean to be rude, but can someone please help me?

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    Default Re: NullPointerException error

    please help!

  8. #8
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    Default Re: NullPointerException error

    Please don't bump threads. I recommend you read the Welcome Announcements, in particular clause F. Moreover, you've provided very little information for us to help. "It doesn't work" could mean a million things. Describe the behavior you expect, and the behavior you receive (suggested reading: How To Ask Questions)

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