double与int类型自动转换

package com.abc.test;public class SumTest {public static void main(String[] args) {//题目A：2+4+6+8+.........+40的和，求java算法sunInteger();//题目B：1/2+1/4+1/6+1/8+.........+1/40的和，求java算法sunDouble01();sunDouble02();}public static void sunInteger(){int sum=0;for (int i = 2; i <=40; i+=2) {sum+=i;}System.out.println("sum:"+sum);}public static void sunDouble01(){int sum=0;for (int i = 2; i <=40; i+=2) {sum+=1/i;}System.out.println("sum:"+sum);}public static void sunDouble02(){double sum=0D;for (double  i = 2; i <=40; i+=2) {sum+=1/i;}System.out.println("sum:"+sum);}}