Fibonacci series program in Java (With and without recursion)

Before we begin to see the code to create the Fibonacci series program in Java using recursion or without it, let's understand what does Fibonacci means.

Fibonacci series is a series of natural numbers where next number is equivalent to the sum of previous two numbers i.e. fn = fn-1 + fn-2.In fibonacci sequence each item is the sum of the previous two. So, you wrote a recursive algorithm, for example, recursive function example for up to 5

fibonacci(5) = fibonacci(4) + fibonacci(3)

fibonacci(3) = fibonacci(2) + fibonacci(1)

fibonacci(4) = fibonacci(3) + fibonacci(2)

fibonacci(2) = fibonacci(1) + fibonacci(0)

The first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, and each subsequent number is the sum of the previous two numbers.

Fibonacci series recursion program in Java

package com.fib;

import java.util.Scanner;

public class fibonacciExample {
	public static void main(String[] args) {
		   Scanner input = new Scanner(System.in);
		  
		   System.out.println("Enter the number to limit Fibonacci series: ");
		   int num = input.nextInt();
		   //loop till the last count
		   for(int i = 1; i <= num; i++){
			   //call Fibonacci function to print sum of last two numbers
		      System.out.print(printFibonacci(i) + " ");
		   }
		   input.close();
		 }
		 
		 
		 // recursion function
		 private static int printFibonacci(int CurrentNumber){
		  //exit condition 
		  if(CurrentNumber == 1 || CurrentNumber == 2){
		   return 1;
		  }
		  return printFibonacci(CurrentNumber - 1) + printFibonacci(CurrentNumber - 2);
		 }

}

Output:

Enter how many numbers are needed in Fibonacci series: 
10
1 1 2 3 5 8 13 21 34 55

In the above code, at first, we are asking the user to enter the number of counts up to which user wants to print the series, using loop we pass the number to "printFibonacci" function and then add last two number using logic (num) + (number-1). Since the first two numbers in the series are 1, 1 so return 1 for both n equals 1 and 2 in the recursive method.

Fibonacci Series program in Java without Recursion

package com.fib;

import java.util.Scanner;

public class fibonacciExample {
	public static void main(String[] args)
	{
		  int i = 1, t1 = 0, t2 = 1;
		  Scanner input = new Scanner(System.in);
		  System.out.println("Enter the number to limit Fibonacci series: ");
		  int num = input.nextInt();
		  System.out.println("First " + num + " terms: ");
		  
		  while (i <= num) {
		   System.out.print(t1 + " ");
		   int sum = t1 + t2;
		   t1 = t2;
		   t2 = sum;
		   i++;
		  }	
		  input.close();
	}
}

Output:

Enter the number to limit Fibonacci series: 
10
First 10 terms: 
0 1 1 2 3 5 8 13 21 34 

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