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I need to insert randomly generated numbers into an array

I have looked through questions with similar words or intentions, but could not find one that would help me.

I created an array using user input, I need to generate numbers between 100 and 10000 and insert them into the array. I created an array, it shows as filled with zeros and I generated random numbers, but I cannot insert the randomly generated numbers into the array.

Here is my code so far.

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();
        }
    }
}
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4 answers 


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


Note:

  • Create Random only once, not every iteration of the double for loop
  • If you want 100 to 10000 (inclusive) it should be nextInt(10000-100+1) + 100

  • Random # nextInt (int n) gives you [0, 9990) or [0, 9989], so the largest value you get from your expression is 9999, not 10000
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array[i][j] = r.nextInt(10000 - 100) + 100;


+1


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You are not assigning the rand element to the array. Your 2nd cycle should be

Random r = new Random();
for(int i = 0; i<rows; i++)
{
    for(int j = 0; j<columns; j++)
    {

        array[i][j] = r.nextInt(900) + 100;
        System.out.print(array[i][j] + " ");
    }
    System.out.println();
}
+1


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You need 3 things,

  • Assign a random value to an array.

  • Use only one nested for loop

    .

  • Don't initialize Random r

    inside a loop.

Try the following:

int[][] array = new int[rows][columns];
Random r = new Random();    
for (int a = 0; a < rows; a++)
    for (int b = 0; b < columns; b++) {
        array[a][b] = r.nextInt(10000 - 100) + 100;
        System.out.print(array[a][b]);
    } 
    System.out.println();
}
+1


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