我正在开发一个项目，根据起始余额（b），利率（IR）和要显示的季度计算银行账户的价值。我的整个代码完美无缺，但最后一部分是确保利率等变量在我教授给我的界限范围内。 如果用户在边界外输入值并再次询问该值，我需要显示错误消息。
例如，要显示的季度数需要大于零，且小于或等于10.
正如您所看到的，几乎所有程序都在do-while循环中。我知道我可以有嵌套循环，但是我可以在我的do-while循环中放置什么才能在这种情况下工作？一个if-else声明？尝试并抓住阻止？另一个循环？
如果我使用了try-catch，那么有人能给我一个如何做到这一点的例子吗？非常感谢你的时间，所有的帮助表示赞赏！以下是我的代码供参考。
import java.util.Scanner;
public class InterestCalculator
{
public static void main(String[] args)
{
Scanner scannerObject = new Scanner(System.in);
Scanner input = new Scanner(System.in);
int quartersDisplayed;
double b, IR;
do
{
Scanner keyboard=new Scanner(System.in);
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
quartersDisplayed = keyboard.nextInt();
System.out.println("Next enter the starting balance. ");
System.out.println("This input must be greater than zero: ");
b = keyboard.nextDouble();
System.out.println("Finally, enter the interest rate ");
System.out.println("which must be greater than zero and less than or equal to twenty percent: ");
IR = keyboard.nextDouble();
System.out.println("You have entered the following amount of quarters: " + quartersDisplayed);
System.out.println("You also entered the starting balance of: " + b);
System.out.println("Finally, you entered the following of interest rate: " + IR);
System.out.println("If this information is not correct, please exit the program and enter the correct information.");
double quarterlyEndingBalance = b + (b * IR/100 * .25);
System.out.println("Your ending balance for your quarters is " + quarterlyEndingBalance);
System.out.println("Do you want to continue?");
String yes=keyboard.next("yes");
if (yes.equals(yes))
continue;
else
break;
}
while(true);
}
}
答案 0 :(得分：1)
所以这里有一些代码可以回答你的问题并帮助你入门。但是，您的逻辑存在与您的问题无关的问题，我将在之后解决。
注意：我已在您的代码中添加了评论。他们中的大多数都以＆＃34;编辑开始：＆＃34;这样你就可以告诉我改变了什么。在所有情况下我都没有使用此前缀，因为其中一些是新代码，而且显然是我的评论
import java.util.Scanner;
public class InterestCalculator {
public static void main(String[] args) {
// EDIT: you already have a scanner defined below with a more meaningful name so I removed this one
// Scanner scannerObject = new Scanner(System.in);
Scanner input = new Scanner(System.in);
//EDIT: defining userResponse outside the loop so we can use it everywhere inside
String userResponse = null;
do {
//EDIT: moved the variables inside the loop so that they are reset each time we start over.
//EDIT: initialize your variable to a value that is invalid so that you can tell if it has been set or not.
int quartersDisplayed = -1;
//EDIT: gave your variables more meaningful names that conform to java standards
double startingBalance = -1, interestRate = -1;
//EDIT: you don't need a second Scanner, just use the one you already have.
// Scanner keyboard = new Scanner(System.in);
do{
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
userResponse = input.next();
try{
quartersDisplayed = Integer.parseInt(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
if(quartersDisplayed <= 0 || quartersDisplayed > 10){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
do{
System.out.println("Enter the starting balance (must be greater than zero): ");
userResponse = input.next();
try{
startingBalance = Double.parseDouble(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
if(startingBalance <= 0){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
do{
System.out.println("Enter the interest rate (greater than zero less than twenty percent): ");
userResponse = input.next();
try{
interestRate = Double.parseDouble(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
//Note: I assume twenty percent is represented as 20.0 here
if(interestRate <= 0 || interestRate > 20){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
System.out.println("You have entered the following amount of quarters: "
+ quartersDisplayed);
System.out.println("You also entered the starting balance of: " + startingBalance);
System.out.println("Finally, you entered the following of interest rate: "
+ interestRate);
System.out.println("If this information is not correct, please exit the program and enter the correct information.");
double quarterlyEndingBalance = startingBalance + (startingBalance * interestRate / 100 * .25);
System.out.println("Your ending balance for your quarters is "
+ quarterlyEndingBalance);
System.out.println("Do you want to continue?");
//EDIT: modified your variable name to be more meaningful since the user's response doesn't have to "yes" necessarily
userResponse = input.next();
// EDIT: modified the logic here to compare with "yes" or "y" case insensitively.
// if (userResponse.equals(userResponse))
if("y".equalsIgnoreCase(userResponse) || "yes".equalsIgnoreCase(userResponse))
continue;
else
break;
} while (true);
现在解决其他问题 - 您的兴趣计算对我来说似乎不正确。您的公式根本不使用quartersDisplayed变量。我假设你每季度都在复利，所以在计算你的结果时你肯定需要使用它。
这可能超出了您的项目范围，但您不应使用double或float数据类型来表示金钱。有关此主题的stackoverflow question有很好的信息。
可能的改进 - 由于您要求用户提供两个double类型的值，您可以创建一个方法来请求double值并调用它两次而不是重复代码。这是一种更好的方法，因为它有助于减少出错的可能性，并使测试和维护更容易。
答案 1 :(得分：0)
你可以在你的do / while循环中做这样的事情：
do
{
Scanner keyboard = new Scanner(System.in);
do
{
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
quartersDisplayed = keyboard.nextInt();
}
while (quartersDisplayed < 1 || quartersDisplayed > 10);
System.out.println("Next enter the starting balance. ");
do
{
System.out.println("This input must be greater than zero: ");
b = keyboard.nextDouble();
}
while (b < 1);
// rest of code ...
}
答案 2 :(得分：0)
使用Scanner#hasNextInt（以及$3的等效项），可以避免抛出异常，因此不需要try-catch子句。我认为一般来说，如果你可以避免尝试，它很好，因为它们很笨拙 - 但我可能是错的。
然而，我的方法是这样的。在你的外部锻炼中，有三个其他的do-while循环来获得三个值。原因是您希望保持循环直到获得正确的值。有关double重要原因的解释涵盖here。
我没有包含您的所有代码，只包含相关部分。以下是我的看法：
keyboard.nextLine()