Arrays.fill() in Java with Examples

Last Updated : 25 Nov, 2024

The Arrays.fill() is a method in the java.util.Arrays class. This method assigns a specified value to each element of an entire array or a specified range within the specified array.

Example:

Now let’s understand this with the below simple example to fill an entire array with a specified value:

import java.util.Arrays;

public class GFG { 
    public static void main(String[] args) {
      
        // Create an array of 5 integers
        int[] arr = new int[5];

        // Fill the entire array with the value 2
        Arrays.fill(arr, 2);

        System.out.println("" + Arrays.toString(arr));
    }
}

Output

[2, 2, 2, 2, 2]

Table of Content

Syntax of Arrays.fill() method
Examples of Arrays.fill() in Java

Java Program to Fill a Specific Range in an Array
Java Program to Fill a 2D Array with a Specific Value
Java Program to Fill a 3D Array with a Specific Value

Syntax of Arrays.fill() method

public static void fill(int[] a, int val)

public static void fill(int[] a, int fromIndex, int toIndex, int val)

Parameters:

a: Array to be filled.
val: Value to assign to each element of the array.
fromIndex: Starting index (inclusive) for filling.
toIndex: Ending index (exclusive) for filling.

Return Type: It does not return any value, but modifies the array directly.

Exceptions:

IllegalArgumentException: Thrown if from_Index > to_Index
ArrayIndexOutOfBoundsException: Thrown if fromIndex or toIndex is outside the valid range (i.e., fromIndex < 0 or toIndex > a.length).

Examples of Arrays.fill() in Java

Java Program to Fill a Specific Range in an Array

In this example, we will be using Arrays.fill() method to update only a specific range of elements within the array and remaining other elements will not change.

// Java program to fill a subarray array with 
// given value
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        
      int arr[] = {2, 2, 2, 2, 2, 2, 2,};

        // Fill from index 1 to index 4
        Arrays.fill(arr, 1, 4, 5);
   
        System.out.println(Arrays.toString(arr));
    }
}

Output

[2, 5, 5, 5, 2, 2, 2]

Java Program to Fill a 2D Array with a Specific Value

In this example, we will use Arrays.fill() method to fill all the elements of each row in a 2D array with a specific value i.e. 5. Here, we will be using a for-each loop to iterate over each row of the array.

// Java program to fill a 2D array with 
// given value
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        
      int [][]arr = new int[2][2];

        // Fill each row with 5 
        for (int[] r : arr)
            Arrays.fill(r, 5);
   
        System.out.println(Arrays.deepToString(arr));
    }
}

Output

[[5, 5], [5, 5]]

Java Program to Fill a 3D Array with a Specific Value

In this example, again we will use Arrays.fill() method to fill each element of a 3D array with a specific value i.e. 2. Here, we will be using Nested loops to fill each row and column in the 3D array.

// Java program to fill a 3D array with 
// given value. 
import java.util.Arrays;

class GFG {
    public static void main(String[] args) {
        
      int[][][] arr = new int[2][2][2];

        // Fill each row with 2 
        for (int[][] r : arr) {
            for (int[] c : r) {
                Arrays.fill(c, 2);
            }
        }

        System.out.println(Arrays.deepToString(arr));
    }
}