2d array help

[nweid1]

I have to write a program for my programming class prints out a table filled with "-"s and randomly fills them with "#"s. So first, I have to create a 2d array where the number of rows and columns are given by the user. Then, I have to print the initial table with all "-"s. So, I created a boolean array with the number of rows and columns as the user input, and make a for loop to set every spot in the array as false. Then I may a loop that says if the spot is false, print out a "-". If I enter a number over 1 for the column or row, it won't work. If I put 1, it runs but doesn't print out. Please help! What am I doing wrong? A sample of the output would be:

Rows: 5
Columns: 8

- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -

Heres the code

public class Matrix2 {
 
import java.util.Random;
import java.util.Scanner;
 
 
	public static void main(String[] args) {
 
		Scanner console = new Scanner(System.in);
		System.out.println("Number of rows?");
		int rows = console.nextInt();
 
		System.out.println("Number of columns?");
		int columns = console.nextInt();
 

		boolean board[][] = new boolean[rows][columns];
 
		for (int i = 0; i < rows; i++) {
			for (int j = 0; j < columns; j++) {
 
				board[rows][columns] = false;
 
			}
		}
 
		for (int i = 0; i < rows; i++) {
			for (int j = 0; j < columns; j++) {
 
				if(board[rows][columns] == false) {
					System.out.print("-");
 
				}
 
			}
			System.out.println();
		}
	}
}

[diamonddragon]

Why i and j are initialized to 1?

for (int i = 1; i < rows; i++) {
            for (int j = 1; j < columns; j++) {

I don't see any random value in code above.

[nweid1]

Good call. I switched them to 0 but it still gives me this error: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException

[diamonddragon]

How do You access element of an array?

[Rameshwar Soni]

for (int i = 0; i < rows; i++) {
			for (int j = 0; j < columns; j++) {
 
				board[rows][columns] = false;
 
			}
		}

Firstly it is not always possible that the user is going to input same number of rows and columns i.e. it can be a irregular 2-dimensional array, therefore
you cannot write your inner for-loop the way you have written. More better way is

for(int i=0; i< rows; i++) 
           {
              for(int j=0; j<board[i].length; j++)
              {   
                        //code
              }
           }

Secondly as said previously by dragon you are accessing your array elements incorrectly inside the for loop, it has to be

board[i][j]

instead of

board[rows][columns]

[diamonddragon]

Firstly it is not always possible that the user is going to input same number of rows and columns i.e. it can be a irregular 2-dimensional array, therefore
you cannot write your inner for-loop the way you have written. More better way is

It's called rugged array.

[Rameshwar Soni]

The question originally posted by user will not have the irregular 2 dimensional array. So the for-loops used by the original user will work but will fail
if he goes for irregular multi-dimensional array.

It's called rugged array.

Do you mean to say Jagged array, which is there in C-sharp?