Why does my output give me the wrong amount of each number?

Question

I am trying to make a program where I can input the size of a 2D array, the highest number in a 2D array, and the most amount of a certain number in the 2D array, and then fill it with random numbers in between 1 and the highest number. In my code, I specify that the max amount of times a number should repeat is 4, yet my output doesn't match that. Any suggestions?

This is my code:

class Main {
    public static void main(String[] args) {
        System.out.println(fill(6, 9, 4));
    }

    public static String fill(int size, int max, int most) {
        int[][] list = new int[size][size];

        int count = 0;

        for (int i = 0; i < list.length; i++) {
            for (int j = 0; j < list[i].length; j++) {
                int x = (int)((Math.random()* max) + 1);
                int y = 0;

                count = 0;
                for (int k = 0; k < list.length; k++) {
                    for (int l = 0; l < list[k].length; l++) {
                        if(list[k][l] == x) count++;
                    }
                }

                if(count < most) {
                    list[i][j] = x;
                } else {
                    while(true) {
                        y = (int)((Math.random()* max) + 1);
                        if(y != x) break;
                    }
                    list[i][j] = y;
                }

                System.out.print(list[i][j] + " ");
            }
            System.out.println();
        }

        return "";
    }
}

And this is my output:

9 4 6 1 9 1 
7 1 4 4 3 2 
6 1 4 2 7 9 
5 9 4 7 2 5 
3 5 3 5 7 4 
3 8 8 6 2 6 

Problem: There are 6 "4"s and 2 "8"s

Answer 1

Your method

while(true) {
    y = (int)((Math.random()* max) + 1);
    if(y != x) break;
}

does not check that count of y did not already reached most

Answer 2

You generate a random number.

You then check if this random number is 'invalid', in the sense that it's been used too many times.

Then, you generate a new random number, check that this isn't the same as your previous number, and then just roll with that . You are failing to check if this number, too, is 'overloaded'. So, what could have happened here is that your algorithm picked '9', counts 9s, finds 4 of them, rolls up a new random number, 9 again, so it rolls yet another number, 4, and just puts 4 in, without checking again.

Rejigger your while loops.

Or, better yet, make a utility class to offload the job of generating a random number, but not a number that's already been returned N times, to a separate class, so that you can untangle this messy code.

Answer 3

Your Issue is here:

while(true) {
    y = (int)((Math.random()* max) + 1);
    if(y != x) break;
}
list[i][j] = y;

This basically just rules out that x will be repeated more than most, but not y.

On a side note, I recommend using hash maps to keep track of the occurrences instead of iterating over the whole array over and over.