IterativeFactor.java

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

public class IterativeFactor {

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

        System.out.println("#####################################################################");
        System.out.println("FACTORIAL: !" + factor);

        Instant before = Instant.now();

        BigDecimal result = new BigDecimal(1);
        for (long i = 1; i <= factor; i++) {
            result = result.multiply(BigDecimal.valueOf(i));
            System.out.println("... " + result);
        }

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


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

}

RecursiveFactor.java

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

public class RecursiveFactor {

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

        System.out.println("#####################################################################");
        System.out.println("FACTORIAL: !" + factor);

        Instant before = Instant.now();

        BigDecimal result = factorial(factor);

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

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


    private static BigDecimal factorial(long factor) {
        if (factor == 0) {
            return BigDecimal.valueOf(1);
        } else {
            BigDecimal result = (BigDecimal.valueOf(factor).multiply(factorial(factor - 1)));
            System.out.println("... " + result);
            return result;
        }
    }
}

Online java compiler:
IterativeFactor.java: https://www.jdoodle.com/a/1Amu
RecursiveFactor.java https://www.jdoodle.com/a/1Amv