Final Arrays in Java

The final keyword makes a variable's reference constant, not its contents. When an array is declared as final, you cannot reassign it to point to a new array. However, you can still modify the elements within the array.

• A final array must be initialized once and cannot be reassigned later.
• Helps maintain a fixed reference, improving code safety and predictability.

Final Array means

If an array is final, it means we can not make it point to a new array, but we can change the elements inside it.

Example: final int[] arr = {10, 20, 30};

Modifying elements inside the array is allowed

arr[2] = 99;

Reassigning the array reference is NOT allowed
arr = new int[]{600, 700, 800}; // Compilation error

Explanation: Here we have declared an array arr as final, which means we can not point arr to a different array, but we can change the value inside the array.

Examples of Final Arrays in Java

Let's now see some examples for better understanding.

Example 1: Modifying Elements of a Final Array

import java.util.*;

class Geeks {
    public static void main(String[] args)
    {

        final int[] arr = {10,20,30};

        arr[2] = 99;

        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
    }
}

10 20 99 

Explanation: The above example shows that we can change the values inside the final array but we can not replace the whole array.

Example 2: Modifying Object State Referenced by a Final Variable

class Geeks {
  
    int p = 20;
    public static void main(String args[])
    {
        final Geeks t = new Geeks();
        t.p = 30;
        System.out.println(t.p);
    }
}

30

Explanation: The above example shows that we can change values inside a final object, but can not replace the object itself.

Example 3: Final Array Reference and Reassignment.

Here is Java Program to Illustrate Reassignment Error in Final Array

// Main class
class Geeks {

    // Main driver method
    public static void main(String args[])
    {
        // Declaring a final array
        final int arr1[] = { 1, 2, 3, 4, 5 };

        // Declaring normal integer array
        int arr2[] = { 10, 20, 30, 40, 50 };

        // Assigning values to each other
        arr2 = arr1;
        arr1 = arr2;

        // Now iterating over normal integer array
        for (int i = 0; i < arr2.length; i++)

            // Printing the elements of above array
            System.out.println(arr2[i]);
    }
}

Output:

Explanation: In the above example, we are trying to change a final array that why we are getting an error.

Example 4: Modifying Elements in a Final Array and Attempting Reassignment

Here is demonstrating how to change value inside a final array

// Import Arrays class for toString() method
import java.util.Arrays; 

public class Geeks {
  
    public static void main(String[] args)
    {
        final int[] numbers = { 1, 2, 3, 4, 5 };

        // Assigning new element into the array
        numbers[0] = 10;
        System.out.println(
            "Array after modifying first element: "
            + Arrays.toString(numbers));
    }
}

Output:

Explanation: The above example shows that we can change the values inside a final array but we can not assign a new array to it.

What we can and cannot do with final arrays and objects in Java: