How to save the matrix in the text file

I just want to input the matrix in the text file, but the result are clearly different. I don’t have any ideas.

public void saveToTextFile() {
    try {
        BufferedWriter writer = new BufferedWriter(new FileWriter(new File("matrix.txt")));

        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                writer.write(matrix[i][j] + " ");
            }
            writer.newLine();
        }
        writer.flush();
        writer.close();

    } catch (IOException e) {
        System.out.println("Error");
    }
}

I expect

1 2 3
4 5 6
7 8 9

but in the file is

1 1 1
5 5 5
9 9 9

Answer

You can try this:

int[][] ints = new int[4][4]; // Let's say you have a 4 * 4 ints array filled like this

        ints[0][0] = 1;
        ints[0][1] = 2;
        ints[0][2] = 3;
        ints[0][3] = 4;

        ints[1][0] = 5;
        ints[1][1] = 6;
        ints[1][2] = 7;
        ints[1][3] = 8;

        ints[2][0] = 9;
        ints[2][1] = 10;
        ints[2][2] = 11;
        ints[2][3] = 12;

        ints[3][0] = 13;
        ints[3][1] = 14;
        ints[3][2] = 15;
        ints[3][3] = 16;

        StringBuilder sb = new StringBuilder(); // String Builder to create the table structure before writing it to the file.

        for (int[] int1 : ints) {
            for (int j = 0; j < int1.length; j++) {
                sb.append(int1[j]).append("t"); // Add tab to delimite the elements
            }
            sb.append("rn"); // Add new line character
        }

        System.out.println(sb);

        Path path = Paths.get("C:\Users\youruser\Documents\test.txt"); // The path to your file

        Files.write(path, sb.toString().getBytes()); // Writes to that path the bytes in the string from the stringBuilder object.

This will print the values like a table: