Why can't I create multitable which has 2 rows and 3 collumns, while I can do the one with 3 rows and 2 collumns?

Like in the code below, I cannot display all the slots in the table, as two of them are missing for whatever reason...?

import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int[][] tab = new int[2][3];
        int number = 1;

        for (int i = 0; i < tab.length; i  ) {
            for (int j = 0; j < tab.length; j  ) {
                tab[i][j] = number  ;
            }
        }
        for (int i = 0; i < tab.length; i  ) {
            for (int j = 0; j < tab.length; j  ) {
                System.out.printf("tab[%d][%d]=%d \n", i, j, tab[i][j]);
            }
        }
    }
}

CodePudding user response：

tab.length will give you the length of first dimension. You should use tab[i].length like below

import java.util.Scanner;

class Main {
public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    int[][] tab = new int[2][3];
    int number = 1;

    for (int i = 0; i < tab.length; i  ) {
        for (int j = 0; j < tab[i].length; j  ) {
            tab[i][j] = number  ;
        }
    }
    for (int i = 0; i < tab.length; i  ) {
        for (int j = 0; j < tab[i].length; j  ) {
            System.out.printf("tab[%d][%d]=%d \n", i, j, tab[i][j]);
        }
    }
}

}

CodePudding user response：

In Java, multidimentional arrays don't actually exist. Instead, an int[][] is just an array with int[].

For example, it is perfectly fine to just do this:

tab[1] = new int[7];

Now the array is not a matrix anymore, as the separate arrays each have different sizes. This is called a jagged array. The 'multidimensional' array now looks like this:

0 0 0
0 0 0 0 0 0 0

In your case, tab.length refers to the length of the outside array. To get the length of each subarray, use tab[i] instead.

CodePudding user response：

Put the length of column based of specific row e.i tab[row].length in inner loop

public static void main(String[] args) {
        
        Scanner scanner = new Scanner(System.in);
        
        int row = 3;  //setting row here
        int col = 4;  // setting column here
        
        int[][] tab = new int[row][col];
        int number = 1;

        for (int i = 0; i < tab.length; i  ) {
            for (int j = 0; j < tab[i].length; j  ) {
                tab[i][j] = number  ;
            }
        }
        for (int i = 0; i < tab.length; i  ) {
            for (int j = 0; j < tab[i].length; j  ) {
                System.out.printf("tab[%d][%d]=%d \n", i, j, tab[i][j]);;
            }
            
        }
    }