# Recursive Fibonacci Sequence in Java

Rashmi Patidar Jan 03, 2023 Apr 06, 2021

## Fibonacci Sequence

A sequence that is formed by the addition of the last two numbers starting from 0 and 1. If one wants to find the nth element, then the number is found by the addition of (n-1) and (n-2) terms, where n must be greater than 0.

## Recursion

Recursion is the process where the same definitive function or procedure calls itself multiple times until it encounters a terminating condition. If we do not specify a terminating condition, the method will enter into an infinite loop state.

## Recursive Fibonacci Sequence in Java

In the code given below, the `main()` method calls a static function `getFibonacciNumberAt()` defined in the class. The function takes a parameter that defines a number, where we want to evaluate the Fibonacci number. The function has a primary check that will return 0 or 1 when it meets the desired condition. Otherwise, the function will again call itself by decrementing the parameter passed to it.

``````package recursiveFibonacci;

public class RecursiveFibonacciSequence {
public static void main(String[] args) {
int fibonacciNumber = getFibonacciNumberAt(6);
System.out.println(fibonacciNumber);
}

public static int getFibonacciNumberAt(int n) {
if (n == 0)
return 0;
else if (n == 1)
return 1;
else
return getFibonacciNumberAt(n - 1) + getFibonacciNumberAt(n - 2);
}
}
``````

Output:

``````8
``````

The detailed evaluation can be seen below :

``````getFibonacciNumberAt(6) = getFibonacciNumberAt(5) + getFibonacciNumberAt(4); //5+3=8
getFibonacciNumberAt(5) = getFibonacciNumberAt(4) + getFibonacciNumberAt(3); //3+2=5
getFibonacciNumberAt(4) = getFibonacciNumberAt(3) + getFibonacciNumberAt(2); //2+1=3
getFibonacciNumberAt(3) = getFibonacciNumberAt(2) + getFibonacciNumberAt(1); //1+1=2
getFibonacciNumberAt(2) = getFibonacciNumberAt(1) + getFibonacciNumberAt(0); //1+0=1
If, getFibonacciNumberAt(1) = 1;
And getFibonacciNumberAt(0) = 0;
``````

We can modify the above program to print a series up to the desired number.

``````package recursiveFibonacci;

public class RecursiveFibonacci {
public static void main(String[] args) {
int maxCount = 10;
for (int i = 0; i <= maxCount; i++) {
int fibonacciNumber = printFibonacci(i);
System.out.print(" " + fibonacciNumber);
}
}

public static int printFibonacci(int n) {
if (n == 0)
return 0;
else if (n == 1)
return 1;
else
return printFibonacci(n - 1) + printFibonacci(n - 2);
}
}
``````

Output:

``````0 1 1 2 3 5 8 13 21 34 55
``````
Note
For calculation of larger numbers, we can use the `BigInteger` class in Java. The recursion process will be complex for larger numbers; hence the computation time for such numbers will also be more.

Rashmi is a professional Software Developer with hands on over varied tech stack. She has been working on Java, Springboot, Microservices, Typescript, MySQL, Graphql and more. She loves to spread knowledge via her writings. She is keen taking up new things and adopt in her career.