Java 8 : Fibonacci Series

Three techniques to implement Fibonacci Series in Java:

1. Fibonacci Series With Iteration Approach
2. Fibonacci Series With Recursion Approach
3. Fibonacci Series With Java 8 Collectors Approach

Fibonacci Series With Iteration Approach Example:

import java.util.Scanner;

public class FibonacciWithIteration
{

public static void main(String[] args)
  {

System.out.println("Enter A Number Upto Which Fibonacci Series You Want = ");

int num = new Scanner(System.in).nextInt();      

       System.out.println("Fibonacci Series With Iteration Approach Upto " + num +" numbers = ");

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

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

        }

}

   public static int fibonacciWithIteration(int num)
    {

        if(num == 1 || num == 2){

            return 1;

        }

        int fibo1=1, fibo2=1, fibonacci=1;

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

            fibonacci = fibo1 + fibo2; 

            fibo1 = fibo2;

            fibo2 = fibonacci;          

        }

        return fibonacci;      

    }   

}

Output:

Enter A Number Upto Which Fibonacci Series You Want = 

4

Fibonacci Series With Iteration Approach Upto 4 numbers = 

1 1 2 3 

Fibonacci Series With Recursion Approach Example:

import java.util.Scanner;

public class FibonacciWithRecursion
{

public static void main(String[] args)
    {

System.out.println("Enter A Number Upto Which Fibonacci Series You Want = ");

int num = new Scanner(System.in).nextInt();      

        System.out.println("Fibonacci Series With Recursion Approach Upto " + num +" numbers = ");

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

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

        }

}

    public static int fibonacciWithRecursion(int num)
    {

    if(num == 1 || num == 2)
        {

            return 1;

        }

      

        return fibonacciWithRecursion(num-1) + fibonacciWithRecursion(num -2);  

    }   

}

Output:

Enter A Number Upto Which Fibonacci Series You Want = 

4

Fibonacci Series With Iteration Approach Upto 4 numbers = 

1 1 2 3 

Fibonacci Series With Java 8 Collectors Approach Example:

import java.util.HashMap;

import java.util.Map;

import java.util.Scanner;

public class FibonacciWithCollectors
{

    private final Map<Integer,Long> cache;

    public FibonacciWithCollectors()
   {

        cache = new HashMap<>();

        cache.put(0, 0L);

        cache.put(1, 1L);

    }

    public long fibonacci(int x)
    {

        return cache.computeIfAbsent(x, n -> fibonacci(n-1) + fibonacci(n-2));

    }

    public static void main(String[] args)
    {

    System.out.println("Enter A Number Upto Which Fibonacci Series You Want = ");

int num = new Scanner(System.in).nextInt();      

        System.out.println("Fibonacci Series With Collectors Approach Upto " + num +" numbers = ");

        FibonacciWithCollectors f = new FibonacciWithCollectors();

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

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

        }

}

}

Output:

Enter A Number Upto Which Fibonacci Series You Want = 

4

Fibonacci Series With Collectors Approach Upto 4 numbers = 

1 1 2 3