Having trouble using java.arraycopy. (ArrayIndexOutofBounds)

Question

I am trying to read a csv file and copy it's data into an array. I can't seem to get it to work this way and I'm not sure why.

String[] row = new String[0];
ArrayList<String[]> csv = new ArrayList<>();

String parser = "SPImages";
CSVReader reader = new CSVReader(new FileReader("C://data.csv"));
String[] nextLine;


while ((nextLine = reader.readNext()) != null){
    System.arraycopy(nextLine, 0, row, 0, nextLine.length);
}

@MrSmith42 Ignore that part. It was a comment for something else I was trying to do. I just forgot to delete it. I will now. — Aaron Lemon
– Aaron Lemon, Commented Jan 30, 2013 at 21:47
@Aaron Lemon: but even when row is big enough for the arraycopy, you will overwrite the content with each loop iteration. — MrSmith42
– MrSmith42, Commented Jan 30, 2013 at 21:48

jfrank · Accepted Answer · 2013-01-30 21:42:45Z

3

Most likely the destination array (in this case "row") is not as big as the source array (in this case "nextLine"). Arrays, unlike Lists, don't auto-resize.

answered Jan 30, 2013 at 21:42

jfrank

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6 Comments

Aaron Lemon Over a year ago

So I should create row after finding the size of nextLine, huh?

zibi Over a year ago

Exactly, your row must be of proper size, as described here: docs.oracle.com/javase/1.5.0/docs/api/java/lang/…

jfrank Over a year ago

Yes, now that the source code has been updated to include the declaration of row, this is the problem. You will need to create "row" anew each time in the loop, or else you will just be copying over your data each time.

MrSmith42 Over a year ago

@Aaron Lemon: or better define it big enough from the beginning.

jfrank Over a year ago

I think he has to create a new instance of row each time through the loop, right? Assuming "row" will be appended to the "csv" variable. If there's just one declaration of "row", that same memory will be overwritten with each line.

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