package com.exercise.coreJava;/** *求2/1+3/2+5/3+8/5+13/8...前20项之和  */public class Sum {    public static void main(String[] args) {        double sum = 0;        double fenZi = 2.0, fenMu = 1.0;        for (int i = 1; i <= 20; i++) {            sum += fenZi / fenMu;            fenMu = fenZi;            fenZi += fenMu;        }        System.out.println("sum="+sum);    }}