Day 19: Interfaces 求整数的因子之和

source: https://www.hackerrank.com/challenges/30-interfaces?h_r=next-challenge&h_v=zen

import java.io.*;
import java.util.*;

interface AdvancedArithmetic{
   int divisorSum(int n);
}

//Write your code here

class Calculator implements AdvancedArithmetic {
    public int divisorSum(int n) {
        int sq = (int)Math.floor(Math.sqrt((double) n));
        List<Integer> seqs = new ArrayList<Integer>();
        Set<Integer> divisors = new HashSet<Integer>();
        for(int i = 1; i <= sq; i++) seqs.add(i);
        seqs.stream().forEach(i -> {
            if(n % i != 0) return;
            divisors.add(i);
            divisors.add(n/i);
        });
        return divisors.stream().reduce(0, (x, y) -> x + y);
    }
}

class Solution {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        scan.close();
        
          AdvancedArithmetic myCalculator = new Calculator();
        int sum = myCalculator.divisorSum(n);
        System.out.println("I implemented: " + myCalculator.getClass().getInterfaces()[0].getName() );
        System.out.println(sum);
    }
}