Prerequisite: Arrays 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 columns in row-1
array_name[] = new data_type[n2] //n2= no. of columns in row-2
array_name[] = new data_type[n3] //n3= no. of columns in row-3
.
.
.
array_name[] = new data_type[nk] //nk=no. of columns 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}
};
OR
int[][] arr_name = {
new int[] {10, 20, 30 ,40},
new int[] {50, 60, 70, 80, 90, 100},
new int[] {110, 120}
};
OR
int[][] arr_name = {
{10, 20, 30 ,40},
{50, 60, 70, 80, 90, 100},
{110, 120}
};
Following are Java programs to demonstrate the above concept.
Java
class Main {
public static void main(String[] args)
{
int arr[][] = new int [ 2 ][];
arr[ 0 ] = new int [ 3 ];
arr[ 1 ] = new int [ 2 ];
int count = 0 ;
for ( int i = 0 ; i < arr.length; i++)
for ( int j = 0 ; j < arr[i].length; j++)
arr[i][j] = count++;
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.
Java
class Main {
public static void main(String[] args)
{
int r = 5 ;
int arr[][] = new int [r][];
for ( int i = 0 ; i < arr.length; i++)
arr[i] = new int [i + 1 ];
int count = 0 ;
for ( int i = 0 ; i < arr.length; i++)
for ( int j = 0 ; j < arr[i].length; j++)
arr[i][j] = count++;
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 5
6 7 8 9
10 11 12 13 14
Example
Java
import java.util.Scanner;
public class JaggedArray {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print( "Enter the number of sub-arrays: " );
int numberOfArrays = scan.nextInt();
int [][] jaggedArray = new int [numberOfArrays][];
for ( int i = 0 ; i < numberOfArrays; i++) {
System.out.print( "Enter the size of sub-array " + (i + 1 ) + ": " );
int sizeOfSubArray = scan.nextInt();
jaggedArray[i] = new int [sizeOfSubArray];
}
for ( int i = 0 ; i < numberOfArrays; i++) {
System.out.println( "Enter the elements of sub-array " + (i + 1 ) + ":" );
for ( int j = 0 ; j < jaggedArray[i].length; j++) {
jaggedArray[i][j] = scan.nextInt();
}
}
System.out.println( "The jagged array is:" );
for ( int i = 0 ; i < numberOfArrays; i++) {
for ( int j = 0 ; j < jaggedArray[i].length; j++) {
System.out.print(jaggedArray[i][j] + " " );
}
System.out.println();
}
scan.close();
}
}
|
Jagged arrays have the following advantages in Java:
- Dynamic allocation: Jagged arrays allow you to allocate memory dynamically, meaning that you can specify the size of each sub-array at runtime, rather than at compile-time.
- Space utilization: Jagged arrays can save memory when the size of each sub-array is not equal. In a rectangular array, all sub-arrays must have the same size, even if some of them have unused elements. With a jagged array, you can allocate just the amount of memory that you need for each sub-array.
- Flexibility: Jagged arrays can be useful when you need to store arrays of different lengths or when the number of elements in each sub-array is not known in advance.
- Improved performance: Jagged arrays can be faster than rectangular arrays for certain operations, such as accessing elements or iterating over sub-arrays, because the memory layout is more compact.
It’s important to note that jagged arrays also have some disadvantages, such as increased complexity in the code and a potentially less readable codebase, so they should be used carefully and appropriately.
Last Updated :
05 Feb, 2023
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