Arrays.fill() in Java with Examples

java.util.Arrays.fill() method is in java.util.Arrays class. This method assigns the specified data type value to each element of the specified range of the specified array.

Syntax:
// Makes all elements of a[] equal to "val"
public static void fill(int[] a, int val)

// Makes elements from from_Index (inclusive) to to_Index
// (exclusive) equal to "val"
public static void fill(int[] a, int from_Index, int to_Index, int val)

This method doesn't return any value.

Exceptions it Throws:
IllegalArgumentException - if from_Index > to_Index
ArrayIndexOutOfBoundsException - if from_Index  a.length

Examples:

We can fill entire array.

// Java program to fill a subarray of given array 
import java.util.Arrays; 
  
public class Main 
{ 
    public static void main(String[] args) 
    { 
        int ar[] = {2, 2, 1, 8, 3, 2, 2, 4, 2}; 
  
        // To fill complete array with a particular 
        // value 
        Arrays.fill(ar, 10); 
        System.out.println("Array completely filled" + 
                  " with 10\n" + Arrays.toString(ar)); 
    } 
} 

Output:

Array completely filled with 10
[10, 10, 10, 10, 10, 10, 10, 10, 10]

We can fill part of array.

// Java program to fill a subarray array with  
// given value. 
import java.util.Arrays; 
  
public class Main 
{ 
    public static void main(String[] args) 
    { 
        int ar[] = {2, 2, 2, 2, 2, 2, 2, 2, 2}; 
  
        // Fill from index 1 to index 4. 
        Arrays.fill(ar, 1, 5, 10); 
     
        System.out.println(Arrays.toString(ar)); 
    } 
} 

Output:

[2, 10, 10, 10, 10, 2, 2, 2, 2]

We can fill a multidimensional array
We can use a loop to fill a multidimensional array.
1)Fill 2D Array

// Java program to fill a multidimensional array with  
// given value. 
import java.util.Arrays; 
  
public class Main 
{ 
    public static void main(String[] args) 
    { 
        int [][]ar = new int [3][4]; 
  
        // Fill each row with 10.  
        for (int[] row : ar) 
            Arrays.fill(row, 10); 
     
        System.out.println(Arrays.deepToString(ar)); 
    } 
} 

Output:

[[10, 10, 10, 10], [10, 10, 10, 10], [10, 10, 10, 10]]

2) Fill 3D Array

// Java program to fill a multidimensional array with  
// given value.  
  
import java.util.Arrays; 
  
class GFG { 
  
    public static void main(String[] args) { 
        int[][][] ar = new int[3][4][5]; 
  
        // Fill each row with -1.  
        for (int[][] row : ar) { 
            for (int[] rowColumn : row) { 
                Arrays.fill(rowColumn, -1); 
            } 
        } 
  
        System.out.println(Arrays.deepToString(ar)); 
    } 
} 

Output:

[[[-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1]], [[-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1]], [[-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1], [-1, -1, -1, -1, -1]]]

Contact Us