Java – I need to insert randomly generated numbers into the array

I examined these questions carefully with similar words or intentions, but it seems that I can't find any questions that can help me

I created an array using user input. I need to generate a number between 100 and 10000 and insert it into the array I created an array, which appears to be filled with zeros, and I generated random numbers, but I don't seem to be able to insert randomly generated numbers into the array

So far, this is my code

import java.util.*;

public class Print2DArray {

    public static void main(String[] args) {

        System.out.println();
        Scanner userInput = new Scanner(system.in);

        System.out.println("Enter the number of rows");
        int rows = userInput.nextInt();

        System.out.println("Enter the number of columns");
        int columns = userInput.nextInt();

        int[][] array = new int[rows][columns];
        for (int a = 0; a < rows; a++)
            for (int b = 0; b < columns; b++)
                array[a][b] = 0;

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                System.out.print(array[i][j]);
                {
                    Random r = new Random();
                    int rand = r.nextInt(10000 - 100) + 100;
                }
            }
            System.out.println();
        }
    }
}

Solution

import java.util.Random;

import java.util.Random;
import java.util.Scanner;

public class QuickTester {

    public static void main(String[] args) {

        Scanner userInput = new Scanner(system.in);

        System.out.print("Enter the number of rows: ");
        int rows = userInput.nextInt();

        System.out.print("Enter the number of columns: ");
        int columns = userInput.nextInt();

        // Create the Random instance once here!
        Random rand = new Random();
        int[][] array = new int[rows][columns];
        for (int a = 0; a < rows; a++)
            for (int b = 0; b < columns; b++)
                array[a][b] = rand.nextInt(10000 - 100) + 100;

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                System.out.print(array[i][j] + " ");
            }
            System.out.println();
        }   
    }
}

Input / output:

Enter the number of rows: 3
Enter the number of columns: 2
574 5286 
1550 5259 
8343 4877

be careful:

>Create random only once, not every iteration of double for loop > if you want 100 to 10000 (inclusive), it needs nextint (10000-100 1) 100 > Random #nextint (int n) to give you [09990] or [09989], so the maximum value you get from the expression is 9999, not 10000