initialize only some elements of array in java

Question

So I want to skip the first and last elements of the array to initialize. What am I doing wrong?

public static void main(String args[]) throws Exception {

    //Write code here
    Scanner sc = new Scanner(System.in);
    System.out.println("Input Rows: ");
    int m = sc.nextInt();
    System.out.println("Input Columns: ");
    int n = sc.nextInt();
    System.out.println("Enter values: ");
    int[][] arr = new int[m][n];

    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            if (arr[i][j] == arr[0][0] || arr[i][j] == arr[m][n]) {
                continue;
            } else {
                arr[i][j] = sc.nextInt();
            }
        }

        System.out.println();
    }
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            System.out.print(arr[i][j] + " ");
        }
        System.out.println();
    }

}

Here is my output:

Input Rows: 
3

Input Columns:
3

Entered Values:

0 0 0 

0 0 0 

0 0 0

Md Johirul Islam · Accepted Answer · 2018-04-04 14:42:18Z

2

You need to change the if condition inside the loop like following:

for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
        if ((i == 0 && j==0) || (i == m -1 && j == n -1)) {
            continue;
        } else {
            arr[i][j] = sc.nextInt();
        }
    }

    System.out.println();
}

answered Apr 4, 2018 at 14:42

Md Johirul Islam

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Comments

Thomas Timbul · Accepted Answer · 2018-04-04 14:43:31Z

2

In this line:

if (arr[i][j] == arr[0][0] || arr[i][j] == arr[m][n]) {

You are testing for the equality of values within your array. You should be comparing whether the indices you are looking at are the beginning or end of the array. That is to say, you want to compare whether (in pseudo code):

i==0 and j==0, OR i==max index in its dimension and j==max index in its dimension

I have deliberately omitted the literal answer, because this looks a tiny bit like homework.

answered Apr 4, 2018 at 14:43

Thomas Timbul

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Comments

marc_s · Accepted Answer · 2025-07-13 20:09:47Z

1

You compare the value of arr[i][j] with the value of arr[0][0]. You should instead compare i==0 && j==0 || i==m -1 && j==n -1

As your array was empty, and as you start the loop, arr[i][j] was equal to arr[0][0], skipping the first element. but for the next loop, arr[i][j] was still empty, and as you compare it to a non-initialised value, it's always true, skipping in each step

public static void main(String args[]) throws Exception {

    //Write code here
    Scanner sc = new Scanner(System.in);
    System.out.println("Input Rows: ");
    int m = sc.nextInt();
    System.out.println("Input Columns: ");
    int n = sc.nextInt();
    System.out.println("Enter values: ");
    int[][] arr = new int[m][n];
    
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            if (i==0 && j==0 || i==m-1 && j==n-1) {
                continue;
            } else {
                arr[i][j] = sc.nextInt();
            }
        }

        System.out.println();
    }
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            System.out.print(arr[i][j] + " ");
        }
        System.out.println();
    }

}

edited Jul 13 at 20:09

marc_s

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answered Apr 4, 2018 at 14:41

Kepotx

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4 Comments

Hypnic Jerk Over a year ago

Id be careful with the order of operations. I suggest using parenthesis appropriately.

Dinesh Solanki Over a year ago

damn! such small mistake. Thanks a lot

Thomas Timbul Over a year ago

Wrong, your condition can't be satisfied, as the loop invariants are i <m and j<n.

Kepotx Over a year ago

@ThomasTimbul thanks, i just remove the brackets forgetting the -1

kailoon · Accepted Answer · 2018-04-04 14:46:12Z

-1

You don't need to check whether the array items are equal, you just want to check whether the row and column are equal to the last and first.

edited Apr 4, 2018 at 14:46

answered Apr 4, 2018 at 14:40

kailoon

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3 Comments

Dinesh Solanki Over a year ago

you can do that for first element but how can you do it for last element?

lexicore Over a year ago

This is not correct. The OP wants to skip elements [0][0] and [m][n]. Your code skips all the [0][*], [*][0], [m][*], [*][n] elements.

kailoon Over a year ago

Yeah, your'e right. I was read that wrong and I thought he wanted to skip the first and last row and columns. Will edit.

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