How to Implement a Custom Vector with Additional Functionality in Java?

// Java Program to  implement a custom
// Vector with additional functionality
import java.io.*;
import java.util.Vector;

// CustomVector class extending Vector
class GFG<E> extends Vector<E> {
    // Method to calculate sum of elements
    public int calculateSum() {
        int sum = 0;
        // Iterating over elements
        for (E element : this) {
            // Checking if element is an Integer
            if (element instanceof Integer) {
                // Adding element to sum
                sum += (Integer) element;
            }
        }
        // Return sum of elements
        return sum;
    }
}

// Driver Class
public class Main {
    // Main Function
    public static void main(String[] args) {
        // Creating an instance of the CustomVector
        GFG<Integer> customVector = new GFG<>();

        // Adding elements to custom vector
        customVector.add(10);
        customVector.add(20);
        customVector.add(30);

        // Calculating the sum using custom method
        int sum = customVector.calculateSum();

        // Displaying the result
        System.out.println("Sum of elements: " + sum);
    }
}