how to take input from user of an multidimentional array?

Question

I am beginner in java i want to take input of an multidimensional array from user using for loop.

i have tried the following code but its giving some thread error.

Scanner input = new Scanner(System.in);
for(i=0;i<2;i++)
{
    for(j=0;j<2;j++)
    {
        a[i][j] = input.nextInt();
        //System.out.println(a[i][j]);
    }
}
}

Scanner input = new Scanner(System.in);
for(i=0;i<2;i++)
{
    for(j=0;j<2;j++)
    {
        int a[i][j] = input.nextInt();
        }
}
}

Exception in thread "main" java.lang.NullPointerException at practice.prac.main(prac.java:16)

Do you want the user to set the size of your matrix or to fill the matrix with numbes? Where is your array declared and initialized? — SuperMario48, Jul 04 '19 at 17:09
@SuperMario48 fill the matriz numbers. Site Didnt allow me to post whole code — Shreyas Deshmukh, Jul 04 '19 at 17:21

score 0 · Answer 1 · answered Jul 04 '19 at 16:57

0

You can do something like this:

Scanner sc = new Scanner(System.in);
System.out.print("Input total row : ");
int row = sc.nextInt();
System.out.print("Input total column : ");
int column = sc.nextInt();

int [][] matrix = new int[row][column];

answered Jul 04 '19 at 16:57

Khaled Jamal

628
1
6
18

It is just taking the count of rows and columns. i am asking how to take elements from user – Shreyas Deshmukh Jul 04 '19 at 17:19

score 0 · Answer 2 · answered Jul 04 '19 at 17:33

int i,j,a[][] = new int[2][2];

Scanner input = new Scanner(System.in);

for(i=0;i<2;i++)
{
    for(j=0;j<2;j++)
    {
        a[i][j] = input.nextInt();
        }
}
for(i=0;i<2;i++)
{
    System.out.print("\n");
    for(j=0;j<2;j++)
    {
        System.out.print(a[i][j] + "\t");
    }
}
}

SuperMario48 · Answer 3 · 2019-07-04T17:48:52.743

An Array needs to be initialized before used. Because an array has fixed size this could be done like this:

int[][] a = new int[2][2];

After that your first loop seems to be ok

Scanner input = new Scanner(System.in);
for(i=0;i<2;i++)
{
    for(j=0;j<2;j++)
    {
        a[i][j] = input.nextInt();
        //System.out.println(a[i][j]);
    }
}
}

And if you want to do it correct you do it like this.

Scanner input = new Scanner(System.in);
    for (int i = 0; i < a.length; i++) {
        for (int j = 0; j < a[i].length; j++) {
            a[i][j] = input.nextInt();
        }
    }
    input.close();

    for (int i = 0; i < a.length; i++) {
        for (int j = 0; j < a[i].length; j++) {
            System.out.print(a[i][j] + "\t");
        }
        System.out.println();
    }

That is wrong usage of arrays:

int a[i][j] = input.nextInt();

how to take input from user of an multidimentional array?

3 Answers3