## February 1, 2022

### Fibonacci Series Java Program

In this post we’ll see a Java program to display Fibonacci series.

Fibonacci series is a series of natural number where next number is the sum of previous two numbers i.e. fn = fn-1 + fn-2. For example

0, 1, 1, 2, 3, 5, 8, 13, 21 ......

Java program for displaying Fibonacci series can be written using-

1. Recursive logic. See example.
2. Non-recursive logic. See example.

### Fibonacci series program using recursion logic

```import java.util.Scanner;

public class FibonacciSeries {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
//user input
System.out.println("Enter length of the Fibonacci series: ");
int num = sc.nextInt();
for(int i = 0; i < num; i++){
System.out.print(displayFibonacci(i) + " ");
}
}

private static int displayFibonacci(int num){
if(num == 0){
return 0;
}
if(num == 1){
return 1;
}
// sum of previous two numbers - calling recursively
return displayFibonacci(num - 1) + displayFibonacci(num - 2);
}
}
```
Output
```Enter length of the Fibonacci series:
10
0 1 1 2 3 5 8 13 21 34
```

### Fibonacci series Java program using iteration

```import java.util.Scanner;

public class FibonacciSeries {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
//user input
System.out.println("Enter length of the Fibonacci series: ");
int num = sc.nextInt();

displayFibonacci(num);
}

private static void displayFibonacci(int num){
int num1 = 0;
int num2 = 1;
int num3 = 0;
for(int i = 0; i <num; i++){
System.out.print(num3+" ");
num1 = num2;
num2 = num3;
num3 = num1 + num2;
}
}
}
```
Output
```Enter length of the Fibonacci series:
15
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
```

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