convert a String array to a 2d array

Question

I have a String array like this

how can i convert this to a 2d array

1 5 5
2 -2 -3
15 -100 20

3 is the size of 2d

public static class convert(String[] lines){
    int n = Integer.parseInt(lines[0]);             
    int[][] matrix = new int[n][n];
    for (int j = 1; j < n; j++) {
        String[] currentLine = lines[j].split(" ");
        for (int i = 0; i < currentLine.length; i++) {
            matrix[j][i] = Integer.parseInt(currentLine[i]);
        }
    }
}

Fix the typo j = 1 ---> j = 0, other than that it's all good. — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Oct 27, 2014 at 3:03
@dasblinkenlight, he would actually have to then change "lines[j].split(" ");" line to "String[] currentLine = lines[j+1].split(" ");" which would be two changes, or he could just leave j alone and change the matrix assignment, please see my answer for more detail! — Devarsh Desai
– Devarsh Desai, Commented Oct 27, 2014 at 3:26

Devarsh Desai · Accepted Answer · 2014-10-27 03:11:27Z

1

Sin,

You have a couple of Off-by-one errors.

Try this:

int n = Integer.parseInt(lines[0]); 
int[][] matrix = new int[n][n];
for (int j = 1; j <= n; j++) {
                String[] currentLine = lines[j].split(" ");
                for (int i = 0; i < currentLine.length; i++) {
                    matrix[j-1][i] = Integer.parseInt(currentLine[i]);
                }
}

Please let me know if you have any questions!

answered Oct 27, 2014 at 3:11

Devarsh Desai

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Comments

nem035 · Accepted Answer · 2014-10-27 04:58:20Z

1

Since arrays are 0-indexed in Java, you should change your loop initialization variable j to start at 0.

Change:

for (int j = 1; j < n; j++) {

to

for (int j = 0; j < n; j++) {

Also, it seems you want a method to do the conversion, not a class so you should remove this from your method signature and put void since you aren't returning anything from the method.

Change:

public static class convert(String[] lines)

To:

public static void convert(String[] lines)

Also, you should use a different variable to iterate through the string array to make things more cleaner. Since you are trying to use j, you can do that to. Instead of initializing j to 1, you initialize it to 0 as I've said and use j+1 as the index for accessing the lines array.

Here is how your code could look like:

public static void convert(String[] lines)
    int n = Integer.parseInt(lines[0]);             
    int[][] matrix = new int[n][n];
    for (int j = 0, k = 1; j < n; j++) {
        String[] currentLine = lines[j + 1].split(" ");
        for (int i = 0; i < currentLine.length; i++) {
            matrix[j][i] = Integer.parseInt(currentLine[i]);
        }
    }
}

edited Oct 27, 2014 at 4:58

answered Oct 27, 2014 at 3:07

nem035

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1 Comment

Sin Nguyen Over a year ago

thanks so much. it worked. the problem is "String[] currentLine = lines[j + 1].split(" ");"

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