How to fill a two Dimensional ArrayList in java with Integers?

Question

I have to create a 2d array with unknown size. So I have decided to go with a 2d ArrayList the problem is I\'m not sure how to initialize such an array or store information.

Answer 1

I'm not sure how to initialize such an array or store information.

Like this for instance:

List> twoDim = new ArrayList>();

twoDim.add(Arrays.asList(0, 1, 0, 1, 0));
twoDim.add(Arrays.asList(0, 1, 1, 0, 1));
twoDim.add(Arrays.asList(0, 0, 0, 1, 0));

or like this if you prefer:

List> twoDim = new ArrayList>() {{
    add(Arrays.asList(0, 1, 0, 1, 0));
    add(Arrays.asList(0, 1, 1, 0, 1));
    add(Arrays.asList(0, 0, 0, 1, 0));
}};

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To insert a new row, you do

twoDim.add(new ArrayList());

and to append another element on a specific row you do

twoDim.get(row).add(someValue);

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Here is a more complete example:

import java.util.*;

public class Test {

    public static void main(String[] args) {

        List> twoDim = new ArrayList>();

        String[] inputLines = { "0 1 0 1 0", "0 1 1 0 1", "0 0 0 1 0" };

        for (String line : inputLines) {
            List row = new ArrayList();

            Scanner s = new Scanner(line);
            while (s.hasNextInt())
                row.add(s.nextInt());

            twoDim.add(row);
        }
    }
}