Unique Java 2D Arraylist

Question

I am trying to create a unique 2d arraylist. The number of columns are fixed and the number of rows should be dynamic. However, for the first column I want to have the type as chars. The rest of the columns should be with int types. Is there a way of doing this? I am using it for Arithmetic compression.

This is what I currently have

    //encoding section
    float low = 0;
    float high = 1;
    float range = high - low;

    List<int[]> rowList = new ArrayList<int[]>();

    rowList.add(new int[] { 1, 2, 3 });
    rowList.add(new int[] { 4, 5, 6 });
    rowList.add(new int[] { 7, 8 });

    for (int[] row : rowList) 
    {
        System.out.println("Row = " + Arrays.toString(row));
    }

enter image description here

You could create a wrapper class that enforces the types. – Kevin Workman Mar 12 '14 at 16:28 — Kevin Workman, Mar 12 '14 at 16:28

Mohammad Najar · Accepted Answer · 2014-03-12T16:36:44.393

1

This is what you want...

List<Object[]> rowList = new ArrayList<Object[]>();

rowList.add(new Object[] { 'a', 5, 6 });
rowList.add(new Object[] { 'b', 5, 6 });
rowList.add(new Object[] { 7, 8 });

for (Object[] row : rowList) 
{
    System.out.println("Row = " + Arrays.toString(row));
}

And the output is

Row = [a, 5, 6]
Row = [b, 5, 6]
Row = [7, 8]

edited Mar 12 '14 at 16:36

answered Mar 12 '14 at 16:30

Mohammad Najar

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I do apologize for the misunderstanding. I wanted the first column rather than row to consist of all characters. – statius Mar 12 '14 at 16:32
Please look at my modification and don't forget the thumbs up. – Mohammad Najar Mar 12 '14 at 16:37
Its perfect! Didn't know we could do it that way. Will give thumbs up! – statius Mar 12 '14 at 16:42

score 0 · Answer 2 · answered Mar 12 '14 at 16:35

Create a class that corresponds to your needs:

public class My2DArray {
    private char[] firstColumn;
    private int[][] otherColumns;

    // + constructor, getters, setters

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for(int row = 0 ; row < firstColumn.length ; ++row) {
            sb.append(firstColumn[row]);
            for(int col = 0 ; col < otherColumns[row].length ; ++col) {
                sb.append(", ").append(otherColumns[row][col]);
            }
            sb.append(System.getProperty("line.separator"));
        }
        return sb.toString();
    }
}

Shouldn't this be done the other way around? Creating a class `Row` that contains a character and an array of integers. Here you assign much responsibility to one class. — Willem Van Onsem, Mar 12 '14 at 20:20

score 0 · Answer 3 · edited May 23 '17 at 12:27

0

The object route is probably the best way for you. Especially since an Arraylist / Arraylist isn't defined for primitives. You would need to use the Integer type.

And even then, you would need 2 array lists, one for the integers and one for the characters.

See this question: Java Vector or ArrayList for Primitives for more about that.

edited May 23 '17 at 12:27

Community

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answered Mar 12 '14 at 17:55

user3411729

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Unique Java 2D Arraylist

3 Answers3