Jagged Array (Ragged Array) in Java

In this post, we will see how to declare and initialize jagged array in Java.

A jagged array, also known as ragged array or “array of arrays”, is an array whose elements are arrays. The elements of a jagged array can be of different dimensions and sizes unlike C-styled arrays that are always rectangular.

We know that a two dimensional array is nothing but an array of single-dimensional arrays. Therefore, it is possible to create a two dimensional array in Java where individual one dimensional arrays has different length.

To illustrate, consider below example which declares a single-dimensional array having three elements, each of which is a single-dimensional array of integers. The first element is an array of 3 integers, the second is an array of 4 integers, and the third is an array of 2 integers. It uses initializers to fill the array elements with values.

import java.util.Arrays;

class JaggedArray
{
	// Program to illustrate Jagged array in Java
	public static void main(String[] args)
	{
		// Declare a jagged array containing three elements
		int[][] arr = new int[3][];

		// Initialize the elements
		arr[0] = new int[] { 1, 2, 3 };
		arr[1] = new int[] { 4, 5, 6, 7 };
		arr[2] = new int[] { 8, 9 };

		// print the array elements
		for (int[] row : arr)
			System.out.println(Arrays.toString(row));
	}
}

import java.util.Arrays;

class JaggedArray

{

// Program to illustrate Jagged array in Java

public static void main(String[] args)

{

// Declare a jagged array containing three elements

int[][] arr = new int[3][];

// Initialize the elements

arr[0] = new int[] { 1, 2, 3 };

arr[1] = new int[] { 4, 5, 6, 7 };

arr[2] = new int[] { 8, 9 };

// print the array elements

for (int[] row : arr)

System.out.println(Arrays.toString(row));

}

Download Run Code

Output:

[1, 2, 3]
[4, 5, 6, 7]
[8, 9]

Below is memory representation of above Jagged array.

Jagged Array

1. If we don’t specify an array initializer, the default value is assigned to each element of the array depending upon the type of array. 0 is default value for int or long or short or byte, null is default value for String and 0.0 is the default value for double or float.

int[][] arr = new int[3][];

// this will initialize the array elements by 0
arr[0] = new int[1];
arr[1] = new int[2];
arr[2] = new int[3];

int[][] arr = new int[3][];

// this will initialize the array elements by 0

arr[0] = new int[1];

arr[1] = new int[2];

arr[2] = new int[3];

2. We can also initialize the array upon declaration like this:

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

int[][] arr = new int[][]

{

new int[] { 1, 2, 3 };

new int[] { 4, 5, 6, 7 };

new int[] { 8, 9 };

};

or we can use the following shorthand form.

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

int[][] arr =

{

new int[] { 1, 2, 3 };

new int[] { 4, 5, 6, 7 };

new int[] { 8, 9 };

};

3. We can also omit the new operator from the elements initialization:

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

int[][] arr =

{

{ 1, 2, 3 },

{ 4, 5, 6, 7 },

{ 8, 9 }

};

References: Jagged Arrays (C# Programming Guide) | Microsoft Docs

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