Fibonacci Series

Fibonacci Series is a series of numbers in which each number is sum of the two preceding numbers. Number in Fibonacci Series is called Fibonacci number. First two number of series are 0 and 1.

For example: 

 0 , 1, 1, 2, 3, 5, 8 ......

So in above series - Third number i.e 1 = 0 + 1 (sum of two preceding number)

                                 Fourth number i.e 2 = 1+1 (sum of two preceding number)

                                 Fifth number i.e 3 = 1+2 (sum of two preceding number) 

and so on ....

How to create Fibonacci Series program in Java?

We can create Fibonacci series in Java using -

1. Programming Loops (iteration)
2. Using recursion function

Using Programming Loop:

Here is a sample program to print Fibonacci series in Java. This program will print first 10 number of Fibonacci series.

package com.techiepappu.java;

/**
 * This Program will print Fibonacci series using loop.
 * @author http://techiepappu.blogspot.com
 */
public class FibonacciSeries1 {

 public static void main(String args[]) {
  int a = 0, b = 1, c, i, max = 10;
  // printing first 2 number in series (i.e 0 and 1)
  System.out.print(a + ", " + b);
  // using java for loop for printing rest of numbers in series.
  for (i = 2; i < max; ++i) {
   c = a + b;
   System.out.print(", " + c);
   a = b;
   b = c;
  }
 }
}

Output:

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Using recursion function:

Recursion function is a type of function which calls itself.Every recursion should have the following characteristics.

1. A base case which have solution (base value) and end the recursion.
2. A way of getting problem closer to the base case.
3. A recursive call.

Give below is a sample program to print Fibonacci series in Java using recursion. This program will print Fibonacci series as per user input.

 package com.java.techiepappu;

import java.util.Scanner;
/**
 * A sample java program to calculate and print Fibonacci series using recursion.
 *
 * @author http://techiepappu.blogspot.com
 */
public class FibonacciSeries2 {

 public static void main(String[] args) {

  int num = 0;
  System.out.println("How many numbers you want to print from Fibonacci series?: ");
  //using scanner class to read user input.
  Scanner sc = new Scanner(System.in);
  int number = sc.nextInt();
  sc.close();
  System.out.println("Fibonacci Series:");
  while (number > num) {
   System.out.println(fibonacci(num));
   num++;
  }
 }

 /**
  * This is a recursive function which returns a number from fibonacci series.
  * @param n
  * @return nth number of fibonacci series.
  */
 public static int fibonacci(int n) {
  if (n == 0 || n == 1)
   return n;
  else
   return fibonacci(n - 1) + fibonacci(n - 2);
 }
}

Output:
 

 How many numbers you want to print from Fibonacci series?: 
10
Fibonacci Series:
0
1
1
2
3
5
8
13
21
34