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up vote 0 down vote favorite

i am trying to make a java application with GUI. i am writing a code that i want to let the User change some data and save these changes on a text file. Before doing that i want to delete the old data that is changed from a list and then rewrite the new data with the last change.if i am missing any class you wanted to see please tell me i will put it online as fast as possible

this is my 

    public void saveChanges(footBall Player, String name, String level,
        int[] scores, int footSize) {

    try {
        if (CompetitorsList.size() != 0) {
            for (Competitors C : CompetitorsList) {

                if (C instanceof footBall) {
                    String Number = Player.playerNumber + "";
                    if (C.getPlayerNumberAsString().equals(Number)) {
                        System.out.println("c");

 //the error hit me here when i try to remove the object from the list the exception error is       java.util.ConcurrentModificationException 
                        CompetitorsList.remove(C);

                    }

                }
            }

            Name NewName = new Name(name);
            System.out.println("Please get in2");
            footBall NewPlayer = new footBall(Player.playerNumber, scores,
                    level, footSize, NewName);

            CompetitorsList.add(NewPlayer);

            SaveOnFile();
        } else {
            System.out.println("No List");
        }

    } catch (Exception ex) {
        System.out.print("testing4");
        System.out.print("something wrong" + ex);
    }

}

this is the SaveOnFile method: public void SaveOnFile() {

    String scoresInString;
    FileWriter fw;
    try {

        fw = new FileWriter("footBall");

        for (Competitors C : CompetitorsList) {
            if (C instanceof footBall) {
                footBall Scores = new footBall();
                scoresInString = Scores.returnScoreAsString(C.scores);
                fw.write(C.playerNumber + ", " + C.name.getFullName()
                        + ", " + C.level + ", " + scoresInString + ","
                        + ((footBall) C).footSize() + "\n");
                fw.write("\r\n");
            }

        }

        fw.close();

    }
    // message and stop if file not found
    catch (FileNotFoundException fnf) {
        System.out.println("File not found ");
        System.exit(0);
    }
    // stack trace here because we don't expect to come here
    catch (IOException ioe) {
        ioe.printStackTrace();
        System.exit(1);
    }
}
share|improve this question

2 Answers 2

up vote 1 down vote accepted

Calling remove() on a collection invalidates all active iterator. Instead, you have to use the Iterator.remove() method:

for(Iterator<Competitors> it = CompetitorsList.iterator(); it.hasNext(); ) {
    Competitors C = it.next();
    if(C instanceof ...) {
        if(C.getPlayerNumberAsString().equals(Number))
            it.remove();
    ...

This way, the iterator() knows about how the collection changes, which otherwise wouldn't be possible since the ArrayList doesn't track the Iterators it generated.

share|improve this answer
    
Thank you for the fast replay i have one more question if you could help me with. the writing file have spaces in it that i dont want is there a way to control that ?? –  dori naji Nov 8 '11 at 23:54
up vote 1 down vote

Alternatively, if you want to use the same "for-next" syntax and not change to the Iterator syntax, collect all the objects to be removed into a temporary collection. e.g.

ArrayList<Competitors> removeThese = new ArrayList<Competitors>();
for (Competitors C : CompetitorsList) {
   if (wantToRemove(C))  // your number logic goes here...
      removeThese.add(C);
}
CompetitorsList.removeAll(removeThese);
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