Terms you'll find helpful in completing today's challenge are outlined below, along with sample Java code (where appropriate).

2D Arrays

Also known as multidimensional arrays, they are very similar to the regular 1D Array data structure we've already discussed.

Consider the following code:

int rowSize = 2;
int colSize = 4;
int[][] myArray = new int[rowSize][colSize];

This creates a matrix where each element, , can be graphically represented as follows:

(0, 0) (0, 1) (0, 2) (0, 3) 
(1, 0) (1, 1) (1, 2) (1, 3) 

You may find it helpful to think of these elements in terms of real-world structures such as the cells in a spreadsheet table.

To fill the array's cells with values, you can use a nested loop. The outer loop represents the matrix's rows and uses as its variable, and the inner loop represents the matrix's columns and uses as its variable. The code below assigns the value of to each element in the 2D array we declared previously:

int count = 0;

for(int i = 0; i < rowSize; i++) {

    for(int j = 0; j < colSize; j++, count++) {
        myArray[i][j] = count;
    }
}

If we print the contents of each row:

for(int i = 0; i < rowSize; i++) {

    // print the row of space-separated values
    for(int j = 0; j < colSize; j++) {
        System.out.print(myArray[i][j] + " ");
    }
    // end of row is reached, print newline
    System.out.println();
}

we'll see the following output:

0 1 2 3 
4 5 6 7 

Additional Language Resources

C++ Arrays (1D and 2D)
Python Nested List Comprehensions

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