1.你写的程序能让客户随意操作吗？误输入数据、不小心做了非常规的操作程序是什么反应？
2.如果向银行贷款10万元，年利率6.5%，期限为10年，那么每月等额本息还款多少？（算复利条件下等额还款金额）
import java.util.Scanner;
public class Calculator4 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner scanner = new Scanner(System.in);
int key=0;
while (key == 0 || key == 1 || key == 2 || key==3 || key==4 || key==5) {
System.out.println("欢迎使用" + "\n计算单利和复利终值，请按1" + "\n计算本金，请按2"
+ "\n股票投资，请按3"
+ "\n计算利率，请按4"
+ "\n计算资产总值，请按5"
+ "\n计算月等额还款金额，请按6"
+ "\n请输入：");
int key1 = scanner.nextInt();
if (key1 == 1) {
Calculator4.DanliandFuli(); // 计算单利和复利
break;
} else if (key1 == 2) {
Calculator4.Principal(); // 计算本金
break;
} else if (key1 == 3) {
Calculator4.Stock(); // 股票投资(计算时间)
break;
} else if (key1 == 4) {
Calculator4.Rate(); // 计算利率
break;
} else if (key1 == 5) {
Calculator4.Assets(); // 计算资产总值
break;
}else if (key1 ==6 ) {
Calculator4.Repayment(); // 计算资产总值
break;
}else {
System.out.println("\n输入错误！请重新输入！");
}
}
}
private static void Repayment() {
// TODO Auto-generated method stub
double sum,i;
int month;
Scanner scanner = new Scanner(System.in);
System.out.print("请输入本金：");
double money = scanner.nextDouble();
System.out.print("请输入年利率：");
double rate = scanner.nextDouble();
System.out.print("请输入贷款年数：");
int years = scanner.nextInt();
i=rate/12;//k为月利率
month=years*12;//month为贷款月数
sum=money*i*Math.pow(1+i, month)/(Math.pow(1+i,month)-1);
System.out.println("每月等额还款金额为："+sum);
}
private static void DanliandFuli() {
// TODO 自动生成的方法存根
double N = 1, sum;
Scanner scanner = new Scanner(System.in);
System.out.println("请输入本金：");
double money = scanner.nextDouble();
System.out.println("请输入存钱年数：");
int years = scanner.nextInt();
System.out.println("请输入年利率：");
double rate = scanner.nextDouble();
sum=money+money*years*rate;
System.out.println("单利计算值为：" + sum);
sum=0;
for (int i = 1; i <= years; i++) {
N = (1 + rate) * N;
}
sum = N * money;
System.out.println("复利计算值为：" + sum);
}
private static void Principal() {
// TODO 自动生成的方法存根
double N = 1, money;
Scanner scanner = new Scanner(System.in);
System.out.println("请输入复利终值：");
double sum = scanner.nextDouble();
System.out.println("请输入存钱年数：");
int years = scanner.nextInt();
System.out.println("请输入年利率：");
double rate = scanner.nextDouble();
for (int i = 1; i <= years; i++) {
N = (1 + rate) * N;
}
money = sum / N;
System.out.println("应投入的本金为：" + money);
}
private static void Stock() {
// TODO 自动生成的方法存根
Scanner scanner = new Scanner(System.in);
System.out.println("请输入本金：");
double money = scanner.nextDouble();
System.out.println("请输入复利终值：");
int sum = scanner.nextInt();
System.out.println("请输入年利率：");
double rate = scanner.nextDouble();
int years=(int) ((Math.log(sum)/Math.log(1+rate))-(Math.log(money)/Math.log(1+rate)));
System.out.println("所需年限为：" + years);
}
private static void Rate() {
// TODO 自动生成的方法存根
double rate;
Scanner scanner = new Scanner(System.in);
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();
rate=sum/(money*years);
System.out.println("利率为：" + rate);
}
private static void Assets() {
// TODO 自动生成的方法存根
double sum;
Scanner scanner = new Scanner(System.in);
System.out.print("请输入本金：");
double money = scanner.nextDouble();
System.out.print("请输入利率：");
double rate = scanner.nextDouble();
System.out.print("请输入存钱年数：");
int years = scanner.nextInt();
sum=money*rate*years;
System.out.println("若投资本金每年固定不变，最后得到的资产总值为：" + sum);
sum=0;
for(int i=1;i<=years;i++){
sum=money*rate*1;
money=sum;
}
System.out.println("若连本带利投资，最后得到的资产总值为：" + sum);
}
}
演示结果：
