Factorials - Java

gistfile1.java

import java.util.stream.IntStream;

public class Factorials {

    public static void main(String[] args) {
        Integer input = Integer.valueOf(args[0]);

        System.out.printf("factorial of %d (v7) = %d\n", input, version7(input));
        System.out.printf("factorial of %d (v8) = %d\n", input, version8(input));
        System.out.printf("factorial of %d (recursive) = %d\n", input, recursive(input));
        System.out.printf("factorial of %d (tailRecursive) = %d\n", input, tailRecursive(input));
    }

    private static Integer version7(Integer input){
        Integer sum = 1;
        for(int i = 1; i <= input; i++) {
            sum = sum * i;
        }
        return sum;
    }

    private static Integer version8(Integer input){
        return IntStream.rangeClosed(1, input).reduce((x, y) -> x * y).getAsInt();
    }

    private static Integer recursive(Integer input){
        if(input == 0)
            return 1;
        else
            return  input  * recursive(input - 1);
    }

    private static Integer tailRecursive(Integer input){
        return  withCount(1, input);
    }

    private static Integer withCount(Integer count, Integer input){
        if(input == 0)
            return count;
        else
            return withCount((count * input), input - 1);
    }

}