2D Arrays Basics

Part of the Logic & Flow section of Coddy's Java journey — lesson 1 of 59.

In Java, a 2D array is an array of arrays, forming a grid or a matrix-like structure. It's like a table with rows and columns, where each cell can hold a value. 2D arrays are useful for representing data that has a two-dimensional relationship, such as a chessboard, a seating chart, or a grid-based game.

Here's how you declare and initialize a 2D array in Java:

data_type[][] arrayName = new dataType[numberOfRows][numberOfColumns];

dataType: The type of elements the array will hold (e.g., int, String, etc.).
arrayName: The name you give to the array.
numberOfRows: The number of rows in the array.
numberOfColumns: The number of columns in the array.

For example, to create a 2D array of integers with 3 rows and 4 columns, you would write:

int[][] matrix = new int[3][4];

You can also initialize a 2D array with values directly:

int[][] matrix = {
	{1, 2, 3},
	{4, 5, 6},
	{7, 8, 9}
};

Challenge

Easy

Initialize a 2D array with the following value:

5, 7, 10, 24, 41
86, 13, 683, 64, 13
42, 46, 791, 111, 9
86, 88, 1845, 5, 15897
9, 1, 5, 5, 6

Cheat sheet

A 2D array in Java is an array of arrays, forming a grid structure with rows and columns.

Declaration and initialization:

data_type[][] arrayName = new dataType[numberOfRows][numberOfColumns];

Example with empty array:

int[][] matrix = new int[3][4];

Initialize with values directly:

int[][] matrix = {
	{1, 2, 3},
	{4, 5, 6},
	{7, 8, 9}
};

Try it yourself

public class Main {
    public static void main(String[] args) {
        int[][] matrix = {
            // Write your code here
        };
            
        
        // Print the matrix
        int rows = matrix.length;
        int cols = matrix[0].length;
        
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
    }
}