Multi Dimensional Array

public class MultidimensionalArrayExample {
    public static void main(String[] args) {
        // Creating a 2D array (3x3 matrix)
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };

        // Accessing elements
        System.out.println(matrix[0][0]); // Prints the element at row 0, column 0 (1)
        System.out.println(matrix[1][2]); // Prints the element at row 1, column 2 (6)
    }
}

Explanation:

1. public class MultidimensionalArrayExample : This line defines the start of a Java class named MultidimensionalArrayExample.
2. public static void main(String[] args) : This is the primary technique that acts as the program’s entry point. Its parameter is an array of strings (args).
3. int[][] matrix = {…};: This line declares and initializes a two-dimensional array named matrix. The array has three rows and three columns, forming a 3×3 matrix. The curly braces {} contain the values for each row.
4. System.out.println(matrix[0][0]);: This line prints the element at the first row (row 0) and the first column (column 0) of the matrix array. In Java, array indices start from 0, so matrix[0][0] accesses the element at the top-left corner of the matrix, which is 1.
5. System.out.println(matrix[1][2]);: This line prints the element at the second row (row 1) and the third column (column 2) of the matrix array. The value at this position is 6.

Output:

Let’s come up with a different array example:

public class MultidimensionalArrayExample {

    public static void main(String[] args) {

        int ages[][];
        ages = new int[4][3];
        ages[0][0] = 34;
        ages[0][1] = 56;
        ages[0][2] = 71;
        ages[1][0] = 67;
        ages[1][1] = 63;
        ages[1][2] = 70;
        ages[2][0] = 23;
        ages[2][1] = 29;
        ages[2][2] = 31;
        ages[3][0] = 17;
        ages[3][1] = 43;
        ages[3][2] = 19;
        // outer loop
        for (int r = 0; r <= 3; r++) {
            // inner loop
            for (int c = 0; c <= 2; c++)
            System.out.print(ages[r][c]);
            System.out.println();
        }
        
    }
}

Explanation:

1. public class MultidimensionalArrayExample: This line defines the start of a Java class named MultidimensionalArrayExample .
2. public static void main(String[] args) : This is the primary technique that acts as the program’s entry point. Its parameter is an array of strings (args).
3. int ages[][];: Declares a 2D array variable named ages without initializing it.
4. ages = new int[4][3];: Initializes the ages array with dimensions 4×3, creating a 2D array capable of holding 4 rows and 3 columns.
5. Subsequent lines set specific values for each element in the ages array, populating it with ages.
6. for (int r = 0; r <= 3; r++) : Begins an outer loop that iterates over the rows (ranging from 0 to 3).
7. for (int c = 0; c <= 2; c++): Starts an inner loop that iterates over the columns (ranging from 0 to 2).
8. System.out.print(ages[r][c] + ” “);: Prints the value of the element at row r and column c, followed by a space.
9. System.out.println();: Prints a newline to move to the next row after each inner loop iteration.

Output:

We can also use the for…each loop to access elements of the multidimensional array. For example,

public class Main {

    public static void main(String[] args) {

        // create a 2d array
        int[][] a = { { 1, -2, 3 }, { -4, -5, 6, 9 }, { 7 }, };

        // first for...each loop access the individual array
        // inside the 2d array
        for (int[] innerArray : a) {
            // the second for...each loop accesses every row element
            for (int data : innerArray) {
                System.out.print(data);
            }
            System.out.println();
        }

    }
}

Explanation:

1. public class MultidimensionalArrayExample: This line defines the start of a Java class named MultidimensionalArrayExample .
2. public static void main(String[] args) : This is the primary technique that acts as the program’s entry point. Its parameter is an array of strings (args).
3. int[][] a = {…};: This line declares and initializes a 2D array named a. The array has three rows, each represented as an array of integers. The first row contains elements {1, -2, 3}, the second row contains elements { -4, -5, 6, 9 }, and the third row contains a single element {7}.
4. for (int[] innerArray : a) {: This starts the first for-each loop. It iterates over each inner array (row) within the 2D array a.
5. for (int data : innerArray) {: This starts the second for-each loop. It iterates over each element data inside the current inner array (row).
6. System.out.print(data);: This prints the value of the current element data without moving to the next line.
7. System.out.println();: This prints a newline character to move to the next line after all elements of the current inner array (row) have been printed.