Arrays.fill() in Java with Examples

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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]]]

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