Jagged Array in Java
In Java, 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.
Example:
arr [][]= { {1,2}, {3,4,5,6},{7,8,9}};
So, here you can check that the number of columns in row1!=row2!=row3. That means the number of columns can be different for different rows.
Pictorial representation of Jagged array in Memory:
Declaration and Initialization of Jagged array :
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 :
// Method 1
int arr_name[][] = new int[][] {
new int[] {10, 20, 30 ,40},
new int[] {50, 60, 70, 80, 90, 100},
new int[] {110, 120}
};
// Method 2
int[][] arr_name = {
new int[] {10, 20, 30 ,40},
new int[] {50, 60, 70, 80, 90, 100},
new int[] {110, 120}
};
// Method 3
int[][] arr_name = {
{10, 20, 30 ,40},
{50, 60, 70, 80, 90, 100},
{110, 120}
};
Examples of Jagged Array in Java
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
arr[0] = new int[3];
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++;
// Printing the Array Elements
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
Example 2:
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 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++;
// 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 5 6 7 8 9 10 11 12 13 14
Example 3:
// Java Program to Implement User
// Defined Jagged Array
import java.util.Scanner;
// Main Class
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();
// Declare the jagged array
int[][] jaggedArray = new int[numberOfArrays][];
// Allocate memory to each sub-array
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];
}
// Initialize the elements of each sub-array
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();
}
}
// Print the elements of the jagged array
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();
}
}
Input:
Enter the number of sub-arrays: 4
Enter the size of sub-array 1: 3
Enter the size of sub-array 2: 4
Enter the size of sub-array 3: 2
Enter the size of sub-array 4: 4Enter the elements of sub-array 1:
1 2 3Enter the elements of sub-array 2:
5 6 7 8Enter the elements of sub-array 3:
6 7Enter the elements of sub-array 4:
1 2 3 4
Output:
The jagged array is:
1 2 3
5 6 7 8
6 7
1 2 3 4
Advantages of using Jagged Array 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.
