Multi-Dimensional Arrays in Java Math.Random - Limiting numbers seperately for each column

Currently, I am in the process of learning how to code. My goal is to develop a software application that generates multiplication questions randomly. In order to achieve this, I would like to restrict the random numbers generated in the first column of the multi-dimensional array to a maximum of 5, and to a maximum of 10 in the second column. I have made some progress in limiting the range of Math.random to 5 or any specified number, but unfortunately, this limitation applies to every column in the array.

Here is my code:

package exercises;

public class TimeTable {
    public static void main(String[] args) {
        int[][] nums = new int[10][2];

        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 2; j++) {
                nums[i][j] = (int) (Math.random() * 5 + 1);
            }
        }

        for (int i = 0; i < 10; i++) {

            System.out.println(nums[i][0] + " x " + nums[i][1] + " = ");

        }
    }
}

and the output is :

3 x 2 = 
1 x 1 = 
5 x 4 = 
2 x 4 = 
5 x 3 = 
1 x 4 = 
5 x 1 = 
2 x 5 = 
3 x 3 = 
5 x 1 = 

From the previous example, it can be observed that the numbers on both sides of the multiplication questions are restricted to a maximum of 5. However, my objective is to limit the first column to a maximum of 5 while allowing the second column to reach a maximum of 10. This will enable children to focus on specific numbers while practicing multiplication.

I have attempted to find solutions by reviewing documentation and searching for previously asked questions on StackOverflow, but I have yet to find a viable solution. Thank you for your assistance.

You don't need a second loop, since they are not doing the same:

    public static void main(String[] args) {
        int[][] nums = new int[10][2];

        for (int i = 0; i < 10; i++) {
            nums[i][0] = (int) (Math.random() * 5 + 1);
            nums[i][1] = (int) (Math.random() * 10 + 1);
        }

        for (int i = 0; i < 10; i++) {
            System.out.println(nums[i][0] + " x " + nums[i][1] + " = ");
        }
    }

Also it's better to create an explicit Random object, because in that case you get access to a more readable API, that does not require casting to int, and you can also create identical sequences by playing around with the seed when creating the random generator:

import java.util.Random;

public class TimeTable {
    public static void main(String[] args) {
        int[][] nums = new int[10][2];
        Random random = new Random(/* you can put a seed here to get identical sequences*/);

        for (int i = 0; i < 10; i++) {
            nums[i][0] = random.nextInt(5) + 1;
            nums[i][1] = random.nextInt(10) + 1;
        }

        for (int i = 0; i < 10; i++) {
            System.out.println(nums[i][0] + " x " + nums[i][1] + " = ");
        }
    }
}

Here is an easy way to do it. Change your array to index columns first, then rows. You don't need a loop to fill the arrays. The formatted print statement helps keep the '=' aligned.

• Random.ints arguments are count, minValue, maxValue (exclusive)

public class TimeTable {
    public static void main(String[] args) {
        int[][] nums = new int[2][]; // length determined by Random
        Random r = new Random();
        nums[0] = r.ints(10, 1, 6).toArray(); // 1 thru 5 inclusive
        nums[1] = r.ints(10, 1, 11).toArray();// 1 thru 10 inclusive
        for (int i = 0; i < nums[0].length; i++) {
            System.out.printf("%d x %-2d = %n", nums[0][i], nums[1][i]);
        }
    }
}

prints

3 x 2  = 
1 x 3  = 
4 x 10 = 
1 x 9  = 
3 x 5  = 
5 x 4  = 
1 x 1  = 
2 x 4  = 
2 x 10 = 
1 x 1  = 

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