Computing Fibonacci Series using Recursion in Java

Recursion means a method; calling directly or indirectly themselves. Recursion is a useful programming technique. In some cases, it enables you to develop a straightforward and simple solution to an otherwise difficult problem. This post introduces you how to Fibonacci Series using Recursion in Java. Actually the Fibonacci series was named for Leonardo Fibonacci, a medieval mathematician.

The Fibonacci Series of  can be defined as follows:

 

    0 1 1 2 3 5 8 13 21 34 55 89 ... 

 

The Fibonacci series begins with 0 and 1, and each subsequent number is the sum of the preceding two. The series can be recursively defined as follows:
 

fib(0) = 0;
fib(1) = 1;
fib(index) = fib(index - 2) + fib(index - 1); index >= 2

 

import java.util.Scanner;

public class CalculateFibonacci {

       public static void main(String args[]) {

              // Create a Scanner

              Scanner input = new Scanner(System.in);

              System.out.print("Enter an index for the Fibonacci number: ");

              int index = input.nextInt();

              System.out.println("Fibonacci number at index " + index + " is "

                           + fib(index));

       }

       /** The method for finding the Fibonacci number */

       public static long fib(long index) {

              if (index == 0) {

                     // Base case

                     return 0;

              } else if (index == 1) {

                     // Base case

                     return 1;

              } else {

                     // Reduction and recursive calls

                     return fib(index - 1) + fib(index - 2);

              }

       }

}

 

 

Output of the above code listing would look like:

 

     Enter an index for the Fibonacci number: 7
   Fibonacci number at index 7 is 13