复利计算1.0,2.0,3.0（java）

程序源代码：
   

 import java.util.Scanner;
    public class ch {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            System.out.println("复利计算器：计算复利终值请按1,计算本金请按2；股票投资：计算时间请按3，计算报酬率请按4，计算资产总值请按5" );
            int num=scanner.nextInt();
            //选择计算对象单利终值
            if (num == 1) {
                double N = 1, sum;
                System.out.print("请输入本金：");
                double money = scanner.nextDouble();
                System.out.print("请输入存钱年数：");
                int years = scanner.nextInt();
                System.out.print("请输入利率：");
                double r = scanner.nextDouble();
                sum = money + money * years * r;
                System.out.println("单利终值为：" + sum);
                sum = 0;
                for (int i = 1; i <= years; i++) {
                    N = (1 + r) * N;
                }
                sum = N * money;
                System.out.println("复利终值为：" + sum);

            }
          //选择计算对象应投入的本金
            if (num == 2) {
                double N = 1, money;
                System.out.print("请输入复利终值：");
                double sum = scanner.nextDouble();
                System.out.print("请输入存钱年数：");
                int years = scanner.nextInt();
                System.out.print("请输入利率：");
                double r = scanner.nextDouble();
                for (int i = 1; i <= years; i++) {
                    N = (1 + r) * N;
                }
                money = sum / N;
                System.out.println("应投入的本金为：" + money);
            }
            //选择计算对象需要时间
            if (num == 3) {
                double years;
                System.out.print("请输入本金：");
                double money = scanner.nextDouble();
                System.out.print("请输入最后得到资产总值：");
                double sum = scanner.nextDouble();
                System.out.print("请输入利率：");
                double r = scanner.nextDouble();        
                years = sum / (money * r);
                System.out.println("时间为（年）：" + years);
            }
            //选择计算对象利率
            if (num == 4) {
                double r;
                System.out.print("请输入本金：");
                double money = scanner.nextDouble();
                System.out.print("请输入最后得到资产总值：");
                double sum = scanner.nextDouble();
                System.out.print("请输入存钱年数：");
                int years = scanner.nextInt();
                r=sum/(money*years);
                System.out.println("利率为：" + r);
            }
            //选择计算对象利率资产总值
            if (num == 5){
                double sum;
                System.out.print("请输入本金：");
                double money = scanner.nextDouble();
                System.out.print("请输入利率：");
                double r = scanner.nextDouble();
                System.out.print("请输入存钱年数：");
                int years = scanner.nextInt();
                sum=money*r*years;
                System.out.println("若投资本金固定不变，则资产总值为：" + sum);
                sum=0;
                for(int i=1;i<=years;i++){
                    sum=money*r*1;
                    money=sum;                
                }
                System.out.println("若连本带利投资，则资产总值为：" + sum);
            }
        }
    }