computeFibonacci.java

import java.util.Scanner;

public class computeFibonacci {

    private static int fibCallCount = 0;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the input for Fibonacci calculation:");
        int n = sc.nextInt();
        
        long result = fib(n);
        System.out.println("Fibonacci of " + n + " is: " + result);
        System.out.println("Number of times fib method was called: " + fibCallCount);
        
        System.out.print("Reverse of 1234 is: ");
        reverseDisplay(1234);
        System.out.println();

        System.out.print("Reverse of 'abcd' is: ");
        reverseDisplay("abcd");
        System.out.println();


        System.out.println("Count of 'a' in 'banana' is: " + count("banana", 'a'));

        System.out.println("Sum of digits of 3311 is: " + sumDigits(3311));
        
        sc.close();
    }

    // Method to compute Fibonacci and count calls
    private static long fib(int n) {
        fibCallCount++;
        if (n <= 1) {
            return n;
        } else {
            return fib(n - 1) + fib(n - 2);
        }
    }

    // Recursive method to reverse display an integer
    public static void reverseDisplay(int value) {
        if (value < 10) {
            System.out.print(value);
        } else {
            System.out.print(value % 10);
            reverseDisplay(value / 10);
        }
    }

    // Recursive method to reverse display a string
    public static void reverseDisplay(String value) {
        if (value.length() <= 1) {
            System.out.print(value);
        } else {
            System.out.print(value.charAt(value.length() - 1));
            reverseDisplay(value.substring(0, value.length() - 1));
        }
    }

    // Recursive method to count occurrences of a character in a string
    public static int count(String str, char a) {
        if (str.length() == 0) {
            return 0;
        } else {
            int count = (str.charAt(0) == a) ? 1 : 0;
            return count + count(str.substring(1), a);
        }
    }

    // Recursive method to sum the digits of a number
    public static int sumDigits(long n) {
        if (n == 0) {
            return 0;
        } else {
            return (int)(n % 10) + sumDigits(n / 10);
        }
    }
}