Nested loop to add data to an Array

Solution 1:

This is what I tried, seem it match with your requirement, you can check it.

    int arr[][] = new int[10][3];
    int i, j;
    int value = 21;
    for(i =0; i <10;i++) {
        for(j = 0; j <3; j++) {
            arr[i][j] = value;
        }
        value +=20;
    }

Solution 2:

The formula you are interested in seems to be ((i + 1) * 20) + 1 which will give you the value at the correct zero based index. Like,

int[][] arr = new int[10][3];
for (int i = 0; i < arr.length; i++) {
    int c = ((i + 1) * 20) + 1;
    for (int j = 0; j < arr[i].length; j++) {
        arr[i][j] = c;
    }
}
System.out.println(Arrays.deepToString(arr));

Outputs (formatted for post)

[[21, 21, 21], [41, 41, 41], [61, 61, 61], [81, 81, 81], 
 [101, 101, 101], [121, 121, 121], [141, 141, 141], 
 [161, 161, 161], [181, 181, 181], [201, 201, 201]]

Note we could use Arrays.fill(int[], int) to fill the array too. Like,

for (int i = 0; i < arr.length; i++) {
    int c = ((i + 1) * 20) + 1;
    Arrays.fill(arr[i], c);
}