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);
	}
}