How to pass parseInt array to previous array?

Question

I've been asked to read a file and take the text in there and convert them to a 2d array. Since Eclipse is a pain and wont open/read my text file, I made a test in the class that uses an individually initialized 2d array. My problem is that I don't know to put the parseInt'ed array back into the new one. Or how to use that to form a new 2d array. Here's my code: public static void main(String[] args) {

    String[][] tester = new String[][] { { "-1 2 3 0" }, { "-1 3 4 0" }, { "-1 3 -4 0" }, { "-1 -3 4 0" } };

    int row = 0;
    int col = 0;
    int count = 0;
    int[][] formula = new int[4][];

    while (count < 4) {
        String temp = tester[row][col];
        String[] charArray = temp.split("\\s+");
        int[] line = new int[charArray.length];

        for (int i = 0; i < charArray.length; i++) {
            String numAsStr = charArray[i];
            line[i] = Integer.parseInt(numAsStr);
            //what to do here??
        }

        row++;
        count++;

    }

    System.out.println(Arrays.deepToString(formula).replace("], ",
     "]\n"));
}
}

I want to generate an array that reads like this:

-1 2 3 0

-1 3 4 0

-1 3 -4 0

-1 -3 4 0

How can I accomplish this?

God, I'm so dense...I can't believe I missed this...Thanks!!!! — teddymv, Feb 02 '18 at 07:02

score 1 · Answer 1 · answered Feb 02 '18 at 06:39

You have to add items to the array formula. Just add formula[count] = line; here:

for (int i = 0; i < charArray.length; i++) {
        String numAsStr = charArray[i];
        line[i] = Integer.parseInt(numAsStr);
        formula[count] = line;
    }

and the output is:

[[-1, 2, 3, 0]
[-1, 3, 4, 0]
[-1, 3, -4, 0]
[-1, -3, 4, 0]]

Select as answer if it worked!

score 1 · Accepted Answer · answered Feb 02 '18 at 06:41

Change the definition of formula like this:

int[][] formula = new int[tester.length][];

You want the formula to have the same number of rows as the tester, right?

Also change your while loop to loop until tester.length instead of a constant 4:

while (counter < tester.length)

Now, after the for loop is where the real business begins:

for (int i = 0; i < charArray.length; i++) {
    String numAsStr = charArray[i];
    line[i] = Integer.parseInt(numAsStr);
}
formula[row] = line; // <------------

During the for loop, you've parsed all the integers in one row of the tester. Now it is time to put the row of integers into formula, isn't it?

Thanks for that, especially the loop and width conditions! – teddymv Feb 02 '18 at 07:04 — teddymv, Feb 02 '18 at 07:04

score 1 · Answer 3 · answered Feb 02 '18 at 06:49

How to read a large text file line by line using Java? Java file to 2D array

Demo

import java.io.File;
import java.util.Arrays;
import java.util.Scanner;
import java.io.IOException;

public class MyFile {
    public static void main(String[] args) throws IOException {

        File file = new File("myFile.txt"); // read file name
        Scanner scan = null;

        int[][] myArray = new int[4][4]; // how many?
        String line = null; // line in .txt
        String[] token = null; // number token

        try {
            scan = new Scanner(file);
            while (scan.hasNextLine()) {
                for (int i = 0; i < 4; i++) { // loop thru row
                    line = scan.nextLine(); // scan line
                    token = line.split(" ");

                    for (int j = 0; j < 4; j++) {
                        myArray[i][j] = Integer.parseInt(token[j]);// loop thru col & parse token int
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        scan.close();
        System.out.println(Arrays.deepToString(myArray)); //fix this
    }
}

dbl · Answer 4 · 2018-02-02T11:18:38.847

I would advice you to use a List where you could store the arrays and then it's easily convertible into int[][]...

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        String test = "-1 2 3 0\n-1 3 4 0\n-1 3 -4 0\n-1 -3 4 0";

        Scanner sc = new Scanner(test);

        //read
        List<int[]> arrayList = new ArrayList<>();

        while (sc.hasNextLine()) {
            arrayList.add(Arrays.stream(sc.nextLine().split(" "))
                    .mapToInt(Integer::parseInt)
                    .toArray());
        }

        //print
        arrayList.forEach(arr -> {
            Arrays.stream(arr).forEach(item -> System.out.print(item + " "));
            System.out.println();
        });

        //convert
        int[][] matrix = new int[arrayList.size()][];
        matrix = arrayList.toArray(matrix);


        //print
        Arrays.stream(matrix).forEach(arr -> {
            Arrays.stream(arr).forEach(item -> System.out.print(item + " "));
            System.out.println();
        });

    }

}

Just beware of the fact that if you have to split it on more then one regex pattern you will have to use a flatmap for each of the lines.

score 0 · Answer 5 · answered Feb 02 '18 at 07:57

0

add formula[row] = line; under the for loop

answered Feb 02 '18 at 07:57

parsa

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How to pass parseInt array to previous array?

5 Answers5