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：