Java函数的灵活性如何？

public class Example {

    public static void main(String[] args) {
        // 参数化函数
        printName("John", "Doe");

        // 返回值
        int sum = addNumbers(1, 2, 3);
        System.out.println("Sum: " + sum);

        // 重载
        double avg = average(10.5, 20.2);
        System.out.println("Average: " + avg);

        // 可变参数
        int[] numbers = {1, 2, 3, 4, 5};
        printArray(numbers);

        // 递归
        int factorial = calculateFactorial(5);
        System.out.println("Factorial: " + factorial);
    }

    public static void printName(String firstName, String lastName) {
        System.out.println("Full name: " + firstName + " " + lastName);
    }

    public static int addNumbers(int... numbers) {
        int sum = 0;
        for (int number : numbers) {
            sum += number;
        }
        return sum;
    }

    public static double average(double x, double y) {
        return (x + y) / 2;
    }

    public static void printArray(int[] numbers) {
        for (int number : numbers) {
            System.out.print(number + " ");
        }
        System.out.println();
    }

    public static int calculateFactorial(int n) {
        if (n == 0) {
            return 1;
        } else {
            return n * calculateFactorial(n - 1);
        }
    }
}

Full name: John Doe
Sum: 6
Average: 15.35
1 2 3 4 5 
Factorial: 120