Java Program for Fibonacci Series (Loop, Recursion)

Write a java program to print the Fibonacci series using loop or recursion.

Fibonacci series is the series that start from 0 as the first element and 1 as the second element and the rest of the nth term is equal to (n-1)th term + (n-2)th term.

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 …

So we in order to implement this, we need to do the following

Take input ‘n‘ from the user which denotes the number of terms in Fibonacci series.
Assign first element a=0 and second element b=1 and third element c = 0.
Output the first two element and loop from 3 to n.
Update c=a+b, a=b and b=c and output the value of c. Reapeat the same steps for each iteration.

Let’s print the Fibonacci series in java using the same steps mentioned above.

Fibonacci Series in Java using Loop

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);

    int n,a=0, b=1, c=0;

    System.out.println("Enter the value of n");
    n = in.nextInt();

    //Output the first and second element
    System.out.print(a+" "+b+" ");

    for(int i=3; i<=n; i++){
      //Always update c first, second a and last b
      c = a+b;
      a = b;
      b = c;
      System.out.print(c+" ");
    }
  }
}

import java.util.Scanner;

class Main {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int n,a=0, b=1, c=0;

System.out.println("Enter the value of n");

n = in.nextInt();

//Output the first and second element

System.out.print(a+" "+b+" ");

for(int i=3; i<=n; i++){

//Always update c first, second a and last b

c = a+b;

a = b;

b = c;

System.out.print(c+" ");

}

Output

Enter the value of n
12
0 1 1 2 3 5 8 13 21 34 55 89

Enter the value of n

0 1 1 2 3 5 8 13 21 34 55 89

Fibonacci Series in Java using Recursion

import java.util.Scanner;

class Main {

  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);

    int n;
    
    System.out.println("Enter the value of n");
    n = in.nextInt();

    for(int i=1; i<=n; i++){
      //For ith term call recursive function
      System.out.print(fibonacci(i)+" ");
    }
    
  }

  //Recursive function to return the nth term of the Fibonacci series
  private static int fibonacci(int n){
    if(n==1){
      return 0;
    }
    else if(n == 2){
      return 1;
    } else {
      return fibonacci(n-2)+fibonacci(n-1);
    }

  }
}

import java.util.Scanner;

class Main {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int n;

System.out.println("Enter the value of n");

n = in.nextInt();

for(int i=1; i<=n; i++){

//For ith term call recursive function

System.out.print(fibonacci(i)+" ");

}

//Recursive function to return the nth term of the Fibonacci series

private static int fibonacci(int n){

if(n==1){

return 0;

}

else if(n == 2){

return 1;

} else {

return fibonacci(n-2)+fibonacci(n-1);

}

Output

Enter the value of n
10
0 1 1 2 3 5 8 13 21 34

Enter the value of n

0 1 1 2 3 5 8 13 21 34

In the above program, we are computing and returning the nth term of the Fibonacci series from the recursive function. In each recursive call, we are doing the same calculation over again as done for the (n-1)th term. So the recursive way of finding the Fibonacci term is not efficient.

To optimize it we can use dynamic programming for Fibonacci series.

If you have any suggestions or doubts then please comment below.

Fibonacci Series in Java using Loop

Fibonacci Series in Java using Recursion

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