第二章第十三题（金融应用：复利值）(Financial application: compound value)
第二章第十三题（金融应用：复利值）(Financial application: compound value)
**2.13（金融应用：复利值）假设你每月向银行账户存100美元，年利率为5%，那么每月利率是0.05/12=0.00417。
第一个月之后，账户上的值就变成：
100 * (1 + 0.00417) = 100.417
第二个月之后，账户上的值就变成：
(100 + 100.417) * (1 + 0.00417) = 201.252
第三个月之后，账户上的值就变成：
(100 + 201.252) * (1 + 0.00417) = 302.507
以此类推。
编写程序显示六个月后账户上的钱数。（在编程练习题5.30中，你将使用循环来简化这里的代码，并能显示任何一个月之后的账户值。）
Enter the monthly saving amount:100
After the sixth month,the account value is $608.81
2.13 (Financial application: compound value) Suppose you save $100 each month in a savings account with annual interest rate 5%. Thus, the monthly interest rate is 0.05/12 = 0.00417.
After the first month, the value in the account becomes
100 * (1 + 0.00417) = 100.417
After the second month, the value in the account becomes
(100 + 100.417) * (1 + 0.00417) = 201.252
After the third month,the value in the account becomes
(100 + 201.252) * (1 + 0.00417) = 302.507
and so on.
Write a program that prompts the user to enter a monthly saving amount and displays the account value after the sixth month. (In Exercise 5.30, you will use a loop to simplify the code and display the account value for any month.)
参考代码：
方法一：
package chapter02;
import java.util.Scanner;
public class Code_13 {
public static void main(String[] args){
Scanner input = new Scanner(System.in);
System.out.print("Enter the monthly saving amount: ");
double save = input.nextDouble();
for(int i = 0;i < 5;i++){
save = (100 + save) * (1 + 0.00417);
}
System.out.format("After the sixth month, the account value is $%.2f",save);
}
}方法二：
package chapter02;
import java.util.Scanner;
public class Code_13another {
public static void main(String[] args) {
double FirstMonthMoney,SecondMonthMoney,
ThirdMonthMoney,FourthMonthMoney,
FifthMonthMoney,SixthMonthMoney,MoneyMonthSaveAmount,
TestAccountValue;
System.out.print("Enter the monthly saving amount:");
Scanner MoneyInput = new Scanner(System.in);
MoneyMonthSaveAmount = MoneyInput.nextDouble();
FirstMonthMoney = 100 * (1 + 0.00417);
SecondMonthMoney = (100 + FirstMonthMoney) * (1 + 0.00417);
ThirdMonthMoney = (100 + SecondMonthMoney) * (1 + 0.00417);
FourthMonthMoney = (100 + ThirdMonthMoney) * (1 + 0.00417);
FifthMonthMoney = (100 + FourthMonthMoney) * (1 + 0.00417);
SixthMonthMoney = (100 + FifthMonthMoney) * (1 + 0.00417);
System.out.println("After the sixth month,the account value is $" + SixthMonthMoney);
MoneyInput.close();
}
}结果显示：
Enter the monthly saving amount:100
After the sixth month,the account value is $608.8181155768638
Process finished with exit code 0