Java n Choose k

[Cory_1]

I am writting a code to show the number of ways we can pick k # of objects from n total # of objects, and order them without repetition(n choose k). I am given the recrusive for

public static long tough(int x, int y) {
    if (x < y) return tough(y, x);
    else if (y <= 0) return 1;
        else { if (x>y) return tough(x-1, y) + tough(x-1, y-1);
            else return tough(x-1, y-1);}}

We are then asked to write a NON-recursive format, which I already have. My only question is, due to a statement the professor said, is there anyway I can rewrite my non-recursive program so that it uses only ONE for loop, and no other loops, so that it has a time complexity of O(n)? Any help or input advice is greatly appreciated.

import java.util.*;
public class KCombination {
    public static void main(String[] args) {
        Scanner in1 = new Scanner(System.in);
        Scanner in2 = new Scanner(System.in);
        System.out.println("Input a number of total objects to choose from: ");
        int n = in1.nextInt();
        System.out.println("Input a select number of objects to choose from the total number of objects: ");
        int k = in1.nextInt();
        int difference = (n-k);
        for (int i = (n-1); i >= 1; i--) {
            n *= i;
        }

        for (int i = (k-1); i >=1; i--) {
            k *= i;
        }

        for (int i = difference-1; i>=1; i--) {
            difference *= i;
        }

        System.out.println("The factorial value of the first input is: " + n +".");
        System.out.println("The factorial value of the first input is: " + k +".");
        System.out.println("The factorial value of the first and second input's difference is: " + difference +".");

        int combination = n/(k*difference);

        System.out.println("The number of ways to order k objects chosen from n total objects, without repetion, is: " + combination +".");
    }
}