如何在java中访问字符串数组的动态数组的元素？

Question

I'm trying to use opencsv ( http://opencsv.sourceforge.net/ ). There are examples included with the download of opencsv. Here's an excerpt of their example for creating a dynamic array:

CSVReader reader = new CSVReader(new FileReader(ADDRESS_FILE));
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
    System.out.println("Name: [" + nextLine[0] + "]\nAddress: [" + nextLine[1] + "]\nEmail: [" + nextLine[2] + "]");
}

The CSV file it reads is as follows:

Joe Demo,"2 Demo Street, Demoville, Australia. 2615",joe@someaddress.com
Jim Sample,"3 Sample Street, Sampleville, Australia. 2615",jim@sample.com
Jack Example,"1 Example Street, Exampleville, Australia. 2615",jack@example.com

If I move the println statement outside of the while loop, I get an error in Eclipse: "Null pointer access: the variable nextLine can only be null at this location."

My guess is that nextLine has a pointer currently pointing to it's last position or past its last position. I think my question is, how do I control that pointer?

Answer 1

You exit the loop, when nextLine == null . Therefore, when you move your println statement out of the loop, nextLine is null . The error "Null pointer access: the variable nextLine can only be null at this location." makes total sense.

To access everything you read after the loop you could do the following:

Add this before you enter the loop:

List<String[]> readLines = new ArrayList<>();

and in the loop do this:

readLines.add(nextLine);

So after the loop you can read all of your read lines out of the readLines list.