Fibonacci Series Program in Java

Fibonacci Series Definition :

Fibonacci series is something like this :

0, 1, 1, 2, 3, 5, 8, 13, 21, 34…….

In this series each term is calculated by adding the previous two terms where the first two terms are 0 and 1.

For example :

Third term = first term + second term = 0 + 1 = 1

Fourth term = second term + third term = 1 + 1 = 2

Fifth term = third term + fourth term = 1 + 2 = 3

And so on……

If we represent this series in Fn than :

F0 = 0

F1 = 1

F2 = F0 + F1

Or in General

Fn = Fn-1 + Fn-2 where n>= 2

Program By using Iteration :

1:  import java.util.Scanner;  
2:    
3:  class FibonacciSeries  
4:  {  
5:    
6:       private void fibonacciSeries(int n)  
7:       {  
8:            int a = 0; //first variable  
9:            int b = 1; //second variable  
10:            int sum;  
11:            System.out.println("The Fibonacci Series is ");  
12:            System.out.print(""+a+" "+b);  
13:            for(int i=1; i<n; i++)  
14:            {  
15:                 sum = a + b;  
16:                 //Here next term which is the sum of previous two is printed  
17:                 System.out.print(" "+sum);  
18:                   
19:                 //first variable takes value of second variable  
20:                 a = b;  
21:                 //second variable takes sum of previous two  
22:                 b = sum;  
23:            }  
24:       }  
25:    
26:       public static void main(String[] args)  
27:       {  
28:              
29:            System.out.println("Enter the no. till you want fibonacci series");  
30:    
31:            Scanner scan = new Scanner(System.in);  
32:            int n = scan.nextInt();  
33:              
34:            //if we have only single term  
35:            if(n==0)  
36:            {  
37:                 System.out.println("The fibonacci Series is \n0");  
38:            }  
39:            //If we want to show two terms  
40:            else if(n==1)  
41:            {  
42:                 System.out.println("The fibonacci Series is \n0 1");  
43:            }  
44:            else  
45:            {  
46:                 FibonacciSeries obj = new FibonacciSeries();  
47:                 obj.fibonacciSeries(n);  
48:            }  
49:              
50:       }  
51:  }  

In the above program we stored the first two terms of the Fibonacci series which are 0 and 1 in two variables (a and b) and print the same if the series you want to calculate is greater than 2.

This program also checks if we want only 1 term or 2 terms in the series and just print the value of variables a or both a and b respectively.

If the series is longer than 2 terms than in the for loop the sum of two variables are calculated and used as a next term which further will be stored in second variable (i.e. b) and second variable value is stored in first variable (i.e. a).

Output :

Program by using Recursion :

Recursion means you called a method from the same method. It basically implemented by the use of stacks.

1:  import java.util.Scanner;  
2:    
3:  public class FibonacciSeriesWithRecursion  
4:  {  
5:       public static void main(String[] args)   
6:       {  
7:            Scanner s = new Scanner(System.in);  
8:           System.out.print("Enter the no. till you want fibonacci series");  
9:                  
10:            //Get the number of terms and stored in variable n  
11:            int n = s.nextInt();  
12:    
13:            FibonacciSeriesWithRecursion obj = new FibonacciSeriesWithRecursion();  
14:                for (int i = 0; i <= n; i++)   
15:            {  
16:                  System.out.print(obj.fibonacci(i) + " ");  
17:                }  
18:         }  
19:    
20:         private int fibonacci(int n)   
21:       {  
22:                if (n == 0)   
23:            {  
24:                  return 0;  
25:                }   
26:            else if (n == 1)   
27:            {  
28:                  return 1;  
29:                }   
30:            else   
31:            {  
32:                 //calling itself with different arguments known as recursion  
33:                  return fibonacci(n - 1) + fibonacci(n - 2);  
34:                }  
35:         }  
36:  }  
37:    

In the above program we uses a method fibonacci which takes the term of series as argument and calculates the sum of previous two terms by calling itself with previous two terms arguments again and again.

Output :