Java program for Fibonacci Series

 class FibonacciSeries {

    int[] dp;

    // Time Complexity O(2^n) and Space Complexity O(n)

    int fibonacci_recursive(int n) {

        if(n <= 1) { //To return 1st and 2nd term

            return n;

        }

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

    }

    // Time Complexity O(n) and Space Complexity O(n)

    int fibonacci_recursive_memoization(int n) {

        if(n <= 1) { //To return 1st and 2nd term

            return n;

        }

        if(dp[n-2] == -1) {

            dp[n-2] = fibonacci_recursive(n-2);

        }

        if(dp[n-1] == -1) {

            dp[n-1] = fibonacci_recursive(n-1);

        }

        dp[n] = dp[n-2] + dp[n-1];

        

        return dp[n];

    }

    // Time Complexity O(n) and Space Complexity O(1)

    int fibonacci_iterative(int n) {

        if(n <= 1) { //To return 1st and 2nd term

            return n;

        }

        int term1 = 0, term2 = 1, sum = n;

        for(int i = 2; i <=n; i++) {

            sum = term1 + term2;

            term1 = term2;

            term2 = sum;

        }

        return sum;

    }

public static void main (String[] args) {

    FibonacciSeries obj = new FibonacciSeries();

    int n = 8;

    System.out.println(obj.fibonacci_recursive(n));

    

    obj.dp = new int[] {-1,-1,-1,-1,-1,-1,-1,-1,-1};

    System.out.println(obj.fibonacci_recursive_memoization(n));

    

    System.out.println(obj.fibonacci_iterative(n));

}

}