IterativeFibonacci

import java.math.BigDecimal;
import java.time.Duration;
import java.time.Instant;
import java.util.Scanner;

public class IterativeFibonacci {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a number:");
        long fib = in.nextLong();

        System.out.println("#####################################################################");
        System.out.println("FIBONACCI: " + fib);

        Instant before = Instant.now();


        BigDecimal i = BigDecimal.valueOf(1);
        BigDecimal j = BigDecimal.valueOf(0);
        BigDecimal t;
        for (long k = 1; k <= fib; k++) {
            t = i.add(j);
            i = j;
            j = t;
            System.out.println("... " + j);
        }
        BigDecimal result = j;

        Instant after = Instant.now();
        long diff = Duration.between(before, after).toMillis();


        System.out.println("RESULT: !" + fib + " = " + result);
        System.out.println("DURATION: " + diff + " milliseconds");
        System.out.println("#####################################################################");
    }

}

RecursiveFibonacci

import java.math.BigDecimal;
import java.time.Duration;
import java.time.Instant;
import java.util.Scanner;

public class RecursiveFibonacci {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a number:");
        long fib = in.nextLong();

        System.out.println("#####################################################################");
        System.out.println("FIBONACCI: !" + fib);

        Instant before = Instant.now();

        BigDecimal result = fibonacci(fib);

        Instant after = Instant.now();
        long diff = Duration.between(before, after).toMillis();

        System.out.println("RESULT: !" + fib + " = " + result);
        System.out.println("DURATION: " + diff + " milliseconds");
        System.out.println("#####################################################################");
    }


    private static BigDecimal fibonacci(long fib) {
        if (fib == 0) {
            return BigDecimal.valueOf(0);
        } else if (fib == 1) {
            return BigDecimal.valueOf(1);
        } else {
            BigDecimal result = fibonacci(fib - 1L).add(fibonacci(fib - 2L));
            System.out.println("... " + result);
            return result;
        }
    }
}

Online java compiler:
IterativeFibonacci.java: https://www.jdoodle.com/a/1BPF
RecursiveFibonacci.java https://www.jdoodle.com/a/1BPO