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  1. #1
    javagirl24 is offline Banned
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    Default Exception in thread "main" java.lang.NullPointerException

    I am getting this exception in the code below for not initializing arraylist.. could someone please help me with this..:(
    this problem is in g[i].v.add(vv);


    class graph
    {

    public ArrayList<Integer[]> v=new ArrayList<Integer[]>();
    public ArrayList<Integer[]> e=new ArrayList<Integer[]>();


    }


    public class main {



    public static void main(String[] args) {

    Integer vv[]=new Integer[2];
    Integer ee[]=new Integer[3];
    graph g[]=new graph[1000];
    int i=-1;
    String t="t";
    String v="v";
    String e="e";
    FileInputStream fstream;
    try {
    fstream = new FileInputStream("graph1.txt");


    DataInputStream in = new DataInputStream(fstream);
    BufferedReader b = new BufferedReader(new InputStreamReader(in));

    String line;

    try {
    while ((line = b.readLine()) != null) {
    StringTokenizer st = new StringTokenizer(line);

    if(t.equals(st.nextToken()))
    {
    i++;

    }
    line = b.readLine();
    System.out.println(line);
    StringTokenizer st1 = new StringTokenizer(line);

    if(v.equals(st1.nextToken()))
    {

    vv[0]=Integer.parseInt(st1.nextToken());
    vv[1]=Integer.parseInt(st1.nextToken());
    g[i].v.add(vv);
    }
    line = b.readLine();
    StringTokenizer st2 = new StringTokenizer(line);

    if(e.equals(st2.nextToken()))
    {
    ee[0]=Integer.parseInt(st2.nextToken());
    ee[1]=Integer.parseInt(st2.nextToken());
    ee[2]=Integer.parseInt(st2.nextToken());
    g[i].e.add(ee);

    }


    }
    } catch (IOException ex) {
    Logger.getLogger(main.class.getName()).log(Level.S EVERE, null, ex);
    }
    } catch (FileNotFoundException ex) {
    Logger.getLogger(main.class.getName()).log(Level.S EVERE, null, ex);
    }

    }}

  2. #2
    Norm's Avatar
    Norm is offline Moderator
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    Default Re: Exception in thread "main" java.lang.NullPointerException

    What variable has a null value?

    Please post the full text of the error message.


    Some bad practices I see are:
    using variable names that are only 1 character long
    having more than one variable with the same name: e & v

    You need to fix those.

    Also use code tags: http://www.java-forums.org/misc.php?do=bbcode#code
    Last edited by Norm; 05-10-2012 at 09:31 PM.
    If you don't understand my response, don't ignore it, ask a question.

  3. #3
    DarrylBurke's Avatar
    DarrylBurke is offline Forum Police
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    Default Re: Exception in thread "main" java.lang.NullPointerException

    Duplicate of http://www.java-forums.org/new-java/...exception.html

    Closing the thread and banning the javagirl24 account.

    db

    THREAD CLOSED
    If you're forever cleaning cobwebs, it's time to get rid of the spiders.

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