Different Ways To Declare And Initialize 2-D Array in Java

Last Updated : 13 Nov, 2024

An array with more than one dimension is known as a multi-dimensional array. The most commonly used multi-dimensional arrays are 2-D and 3-D arrays. We can say that any higher dimensional array is an array of arrays.

A very common example of a 2D Array is Chess Board. A chessboard is a grid containing 64 1x1 square boxes. You can similarly visualize a 2D array. In a 2D array, every element is associated with a row number and column number. Accessing any element of the 2D array is similar to accessing the record of an Excel File using both row number and column number. 2D arrays are useful while implementing a Tic-Tac-Toe game, Chess, or even storing the image pixels.

Example:

Java

import java.io.*;

class GFG {
    public static void main(String[] args){
      
        int n = 80, m = 5;
        int[][] arr = new int[n][m];

        // initializing the array elements using for loop
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                arr[i][j] = i + j;
            }
        }

        // printing the first three rows of marks array
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < m; j++)
                System.out.printf(arr[i][j] + " ");
            System.out.println();
        }
    }
}

Output

0 1 2 3 4 
1 2 3 4 5 
2 3 4 5 6

Note: We can use arr. length function to find the size of the rows (1st dimension), and arr[0].length function to find the size of the columns (2nd dimension).

Declaring 2-D array in Java

Any 2-dimensional array can be declared as follows:

Syntax:

// Method 1
data_type array_name[][];
// Method 2
data_type[][] array_name;

data_type: Since Java is a statically-typed language (i.e. it expects its variables to be declared before they can be assigned values). So, specifying the datatype decides the type of elements it will accept. e.g. to store integer values only, the data type will be declared as int.

array_name: It is the name that is given to the 2-D array. e.g. subjects, students, fruits, department, etc.

Note: We can write [ ][ ] after data_type or we can write [ ][ ] after array_name while declaring the 2D array.

Initialize 2-D array in Java

data_type[][] array_Name = new data_type[row][col];

The total elements in any 2D array will be equal to (row) * (col).

row: The number of rows in an array
col: The number of columns in an array.

When you initialize a 2D array, you must always specify the first dimension(no. of rows), but providing the second dimension(no. of columns) may be omitted. Java compiler is smart enough to manipulate the size by checking the number of elements inside the columns.

// Incorrect Statement
int[][] arr = new int[][3];
// Correct Statement
int[][] arr = new int[2][];

You can access any element of a 2D array using row numbers and column numbers.