如果一个已声明的大小为n的数组被部分填充，我如何才能找到它的元素数？

def count_elements(arr):
    count = 0
    for element in arr:
        if element is not None:
            count += 1
    return count

# 示例用法
array = [1, None, 3, None, 5]
element_count = count_elements(array)
print("数组中的元素数为:", element_count)

public class ArrayElementCounter {
    public static int countElements(Object[] arr) {
        int count = 0;
        for (Object element : arr) {
            if (element != null) {
                count++;
            }
        }
        return count;
    }

    // 示例用法
    public static void main(String[] args) {
        Object[] array = {1, null, 3, null, 5};
        int elementCount = countElements(array);
        System.out.println("数组中的元素数为: " + elementCount);
    }
}

#include <iostream>

int countElements(int arr[], int size) {
    int count = 0;
    for (int i = 0; i < size; i++) {
        if (arr[i] != NULL) {
            count++;
        }
    }
    return count;
}

// 示例用法
int main() {
    int array[] = {1, NULL, 3, NULL, 5};
    int size = sizeof(array) / sizeof(array[0]);
    int elementCount = countElements(array, size);
    std::cout << "数组中的元素数为: " << elementCount << std::endl;
    return 0;
}