WHILE循环中的布尔语句没有意义吗？

Question

我的while声明对我来说似乎没有任何意义，即使它可行。
我希望它仅在countYears 小于 timeLimit的情况下才计算利息。...因此，如果将timeLimit设置为5，则它应该仅计算5年的利息，但以我读取当前while语句的方式，似乎没有这么说。 也许我只是读错了？

public class RandomPractice {
public static void main(String[] args)
{
    Scanner Keyboard = new Scanner(System.in);
    double intRate, begBalance, balance;
    int countYears, timeLimit;

    System.out.println("Please enter your current investment balance.");
    begBalance = Keyboard.nextDouble();

    System.out.println("Please enter your YEARLY interest rate (in decimals).");
    intRate = Keyboard.nextDouble();

    System.out.println("Please enter how long (in years) you would like to let interest accrue.");
    timeLimit = Keyboard.nextInt();

    balance = begBalance * (1 + intRate);
    countYears = 0;

    /* The way I read this while statement is as follows 
     * "While countYears is GREATER than the timeLimit...calculate the balance"
     * This makes no logical sense to me but I get the correct output? 
     * I want this code to calculate the investment interest ONLY as long as
     * countYears is LESS than timeLimit **/
    while (countYears >= timeLimit)
    {
        balance = balance + (balance * intRate);
        countYears++;
    }       

    System.out.println(balance);

  }
}

Answer 1

您所拥有的代码无法生成正确的数据，我的成绩单以每年1％的速度记录了八年：

Please enter your current investment balance.
100
Please enter your YEARLY interest rate (in decimals).
.01
Please enter how long (in years) you would like to let interest accrue.
8
101.0

换句话说，只增加了一年的利息，而不是八年。

因此，或者您的编译器完全是搞砸了，您的代码不是您想像的那样，或者您用来检查兴趣度计算的任何测试数据和/或方法都有些缺乏。

首先，正如您所countYears < timeLimit那样，您需要将条件更改为countYears < timeLimit 。

此外，您还需要在循环之前删除初始利息计算，因为这意味着您存入钱后将获得全年的利息。 有了这两个更改：

balance = begBalance;
while (countYears < timeLimit) {
    balance = balance + (balance * intRate);
    countYears++;
}       

然后您将获得正确的值 ：

Please enter your current investment balance.
100
Please enter your YEARLY interest rate (in decimals).
.01
Please enter how long (in years) you would like to let interest accrue.
8
108.28567056280801

Answer 2

如果将循环切换为<= ，则根本不会执行循环，这是正确的。

现在，您的输出是在循环外部计算的结果。