程序不打印矩阵中素数的正确总和值

Question

I am a beginner in the java language. I was tasked to create a matrix that calculates the total sum of all prime numbers from the randomly-generated numbers present in the matrix. However, my program does not print the correct value at all. What seems to be the problem with my code?

public static void main(String[] args) {
    int arr[][] = new int[5][5];
    Random ran = new Random();

    System.out.println("Print matrix");
    for (int i = 0; i < arr.length; i++) {
        for (int j = 0; j < arr.length; j++) {
            arr[i][j] = 10 + ran.nextInt(50 - 10 + 1);
            System.out.print(arr[i][j] + "\t");
        }
        System.out.println();
    }
    int sum = 0;
    for (int i = 0; i < arr.length; i++) {
        for (int j = 0; j < arr.length; j++) {
            int num = 0;
            for (int k = 1; k <= arr[i][j]; ++k)
                if (arr[i][j] % k == 0)
                    num++;
            if (num == 2)
                sum = sum + arr[i][j];
        }
    }
    System.out.println("\nPrint the sum of prime no. in the matrix: " + sum);
}

Output:

Print matrix
33  11  41  43  38  
32  18  25  16  24  
40  16  11  18  11  
49  37  22  13  17  
10  45  30  13  37  

Print the sum of prime no. in the matrix: 234

The correct sum value should be 283 instead of 234 .

Answer 1

49 is not prime = 7 * 7 = 49

For the input in the question, 234 is correct answer. 11 + 41 + 43 + 11 + 11 + 37 + 13 + 17 + 13 + 37

For the input in the image, expected result is correct 11 + 47 + 19 + 17 + 41 + 29 + 37 = 201

Possible correction

1. Unless the matrix is a square matrix, it better to use the inner loop as j < arr[i].length
2. Prime number check requires division only till floor(sqrt(num))