通过二维数组中随机生成的数字打印字符数

Question

I was wondering how to go about randomly generating a number, and then having it print that number as a character. This is what I have so far.

import java.util.Scanner;
public class Main
{
    public static void main (String[] args){
    Scanner scan = new Scanner(System.in);

    int[][] ground = new int[12][12];
    int mineNum;

    System.out.print ("Please Enter an Integer");

    int num = scan.nextInt();

    if(num > -1 && num <145){
        for (int i=0; i<ground.length; i++){
            for (int j = 0; j < ground[i].length;j++){
                ground[i][j] = mineNum;
            }
        }
    }
}

I'm thinking that you definitely have to have the random int stored in a variable. But from there I want to have the random int's that the user put in and translate that as X', and input those x's randomly into the array, so I would have to translate that number into number of char, and then insert it randomly into the array with another for? The idea is to look something like , for example, say mineNum is 5, it would look something like this once printed for a 3x9 grid.

0 0 0 0 X 0 X 0 0

0 0 X 0 0 0 0 0 0

0 0 0 0 XX 0 0 0

Answer 1

One option would be to generate 5 distinct random numbers within the dimensions of your 2D grid which would represent Xs. Then fill everything else with Os. I generate random numbers between 0 and dim^2 - 1 . Then I add them to a set until the desired number of random positions has been reached. Finally, I convert those numbers to x/y dimensions to place the Xs onto the board.

Scanner scan = new Scanner(System.in);

int dim = 5;
char[][] ground = new char[dim][dim];
Set<Integer> xSet = new HashSet<>();

System.out.print ("Please Enter an Integer");
int mineNum = scan.nextInt();

Random rand = new Random();
while (xSet.size() < mineNum) {
    int randomNum = rand.nextInt(dim*dim);
    xSet.add(randomNum);
}

// default everything to being Os
for (int r=0; r < dim; ++r) {
    for (int c=0; c < dim; ++c) {
        ground[r][c] = 'O';
    }
}

// then overwrite with Xs
for (int num : xSet) {
    int x = num % dim;
    int y = num / dim;
    ground[x][y] = 'X';
}

System.out.println(Arrays.deepToString(ground).replace("], ", "]\n").replace("[[", "[").replace("]]", "]"));

[O, O, O, O, O]
[O, O, O, X, X]
[O, O, X, O, O]
[O, O, X, O, O]
[O, O, O, X, O]

Demo