Jagged Array in Java

16 May

Jagged Array in Java

A jagged array is an array of arrays such that member arrays can be of different sizes, i.e., we can create a 2-D array but with a variable number of columns in each row. These types of arrays are also known as Jagged arrays.

Pictorial representation of Jagged array in Memory:

Jagged_array

Declaration and Initialization of Jagged array :

Syntax: data_type array_name[][] = new data_type[n][]; //n: no. of rows
array_name[] = new data_type[n1] //n1= no. of colmuns in row-1
array_name[] = new data_type[n2] //n2= no. of colmuns in row-2
array_name[] = new data_type[n3] //n3= no. of colmuns in row-3
.
.
.
array_name[] = new data_type[nk] //nk=no. of colmuns in row-n

Alternative, ways to Initialize a Jagged array :

int arr_name[][] = new int[][] {
new int[] {10, 20, 30 ,40},
new int[] {50, 60, 70, 80, 90, 100},
new int[] {110, 120}
};

int[][] arr_name = {
new int[] {10, 20, 30 ,40},
new int[] {50, 60, 70, 80, 90, 100},
new int[] {110, 120}
};

int[][] arr_name = {
{10, 20, 30 ,40},
{50, 60, 70, 80, 90, 100},
{110, 120}
};
Following are Java programs to demonstrate the above concept.

// Program to demonstrate 2-D jagged array in Java
class Main {
public static void main(String[] args)
{
// Declaring 2-D array with 2 rows
int arr[][] = new int[2][];

// Making the above array Jagged

// First row has 3 columns
arr[0] = new int[3];

// Second row has 2 columns
arr[1] = new int[2];

// Initializing array
int count = 0;
for (int i = 0; i < arr.length; i++)
for (int j = 0; j < arr[i].length; j++)
arr[i][j] = count++;

// Displaying the values of 2D Jagged array
System.out.println("Contents of 2D Jagged Array");
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < arr[i].length; j++)
System.out.print(arr[i][j] + " ");
System.out.println();
}
}
}
Output
Contents of 2D Jagged Array
0 1 2
3 4
Following is another example where i’th row has i columns, i.e., the first row has 1 element, the second row has two elements and so on.

// Another Java program to demonstrate 2-D jagged
// array such that first row has 1 element, second
// row has two elements and so on.
class Main {
public static void main(String[] args)
{
int r = 5;

// Declaring 2-D array with 5 rows
int arr[][] = new int[r][];

// Creating a 2D array such that first row
// has 1 element, second row has two
// elements and so on.
for (int i = 0; i < arr.length; i++)
arr[i] = new int[i + 1];

// Initializing array
int count = 0;
for (int i = 0; i < arr.length; i++)
for (int j = 0; j < arr[i].length; j++)
arr[i][j] = count++;

Course Curriculum

Jagged Array in Java