Fibonacci series in Java

In fibonacci series, next number is the sum of previous two numbers for example 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55 etc. The first two numbers of fibonacci series are 0 and 1.

There are two ways to write the fibonacci series program in java :

* Fibonacci Series without using recursion
* Fibonacci Series using recursion

Fibonacci Series in Java without using recursion :

Program :

import java.util.Scanner;

public class FibonacciSeries {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the number of terms: ");
        int n = input.nextInt();

        int firstTerm = 0, secondTerm = 1;
        System.out.print("Fibonacci series: " + firstTerm + " " + secondTerm + " ");

        for (int i = 3; i <= n; i++) {
            int nextTerm = firstTerm + secondTerm;
            System.out.print(nextTerm + " ");
            firstTerm = secondTerm;
            secondTerm = nextTerm;
        }
    }
}

Output :

Enter the number of terms: 20
Fibonacci series: 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181

In this program, we first ask the user to input the number of terms in the Fibonacci series using the Scanner class. Then, we initialize two variables firstTerm and secondTerm to 0 and 1, respectively, which are the first two terms in the Fibonacci series.

We then print the first two terms using System.out.print().

Next, we use a for loop to generate the remaining terms in the series. We do this by calculating the sum of the previous two terms and storing it in a variable nextTerm. We then print nextTerm to the console using System.out.print(), and update the values of firstTerm and secondTerm to prepare for the next iteration of the loop.

Finally, we use System.out.println() to print a new line to the console at the end of the program.

Fibonacci Series using recursion in java :

Program :

import java.util.Scanner;

public class FibonacciSeries {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the number of terms: ");
        int n = input.nextInt();

        System.out.print("Fibonacci series: ");
        for (int i = 0; i < n; i++) {
            System.out.print(fibonacci(i) + " ");
        }
    }

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

Output :

Enter the number of terms: 20
Fibonacci series: 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181

In this program, we first ask the user to input the number of terms in the Fibonacci series using the Scanner class. Then, we use a for loop to generate each term in the series using the fibonacci() method.

The fibonacci() method is a recursive function that takes an integer argument n and returns the nth term in the Fibonacci series. If n is 0 or 1, we return the corresponding value of 0 or 1. Otherwise, we recursively call the fibonacci() method to calculate the sum of the previous two terms.

Finally, we use System.out.print() to print each term in the Fibonacci series to the console, separated by a space.