【发布时间】：2012-02-24 03:47:10
【问题描述】：
我已经编辑了这个问题，但是在程序的底部我尝试编写一个 switch 语句来验证一些代码。我试图要求用户输入 Y/N 以继续。如果他们输入 Y，程序应该重新启动。如果他们输入 N 程序应该结束。如果他们输入 Z，他们应该会收到一条错误消息，并再次提示 continue y/n? 现在，如果我输入了一个随机字母，我会被发送回数据输入部分，但我不知道为什么。
我还注意到我的计算是错误的。我假设这与我没有使用 bigdecimal 类的事实有关。目前，如果我输入 5.6 作为百分比，它会自动假定它是 560%
我是 Java 新手，不幸的是，我在苦苦挣扎。昨晚有人很好地帮助了我，但没有公然给我答案，我很感激，因为它让我自己解决问题。
非常感谢任何帮助，因为我在这门课上遇到了困难。
import java.util.Scanner;
import java.text.NumberFormat;
public class LoanCalculator
{
public static double getDoubleWithinRange(Scanner sc, String prompt, double min, double max) //validate double
{
double d = 0;
boolean isValid = false;
while(isValid == false)
{
System.out.println(prompt); //print prompt for double
if (sc.hasNextDouble())
{
d = sc.nextDouble();
if (d <= min) //if input <= minimum double
{
System.out.println("Error! Number must be greater than " + min);
System.out.println();//print error grater than min double
}
else if (d >= max) // if input >= maximum double value
{
System.out.println("Error number must be less than " + max);
System.out.println();//print error less than max double value
}
else
isValid = true; //else double is valid
}
else
{
System.out.println("Error! Invalid decimal value.");
System.out.println();
sc.nextLine();
}
}
return d; //return double
}
//validate integer
public static int getIntWithinRange(Scanner sc, String prompt, int min, int max)
{
int i = 0;
boolean isValid = false;
while(isValid == false)
{
System.out.println(prompt); //print prompt for integer
if (sc.hasNextInt())
{
i = sc.nextInt();
if (i <= min) //if input <= minimum integer
{
System.out.println("Error! Number must be greater than " + min);
System.out.println();//print error grater than min integer
}
else if (i >= max) // if input >= maximum integer value
{
System.out.println("Error number must be less than " + max);
System.out.println();//print error less than max integer value
}
else
isValid = true; //else integer is valid
}
else
{
System.out.println("Error! Invalid integer value.");
System.out.println();
sc.nextLine();
}
}
return i; //return integer
}
public static void main(String[] args)
{
System.out.println("Welcome to the loan calculator"); //welcome user to loan calculator
Scanner sc = new Scanner(System.in); // create new scanner
String choice = "y"; //start choice loop
while (choice.equalsIgnoreCase("y"))
{
System.out.println();
System.out.println("DATA ENTRY");
double loanAmount = getDoubleWithinRange(sc, "Enter loan amount: ", 0.0, 1000000.0); //get user input for loanAmount
//get user input for interestRate
double interestRate = getDoubleWithinRange(sc, "Enter yearly interest rate: ", 0, 20);
//get user input for years
int years = getIntWithinRange(sc, "Enter number of years: ", 0, 100);
int months = years * 12; // calculate years to months
//calculate monthly payment
double monthlyPayment = loanAmount * interestRate/ (1 - 1 / Math.pow(1 + interestRate, months));
//import currency instance
NumberFormat currency = NumberFormat.getCurrencyInstance();
// import percent instance
NumberFormat percent = NumberFormat.getPercentInstance();
percent.setMinimumFractionDigits(1); //set fraction digits for percent
System.out.println("RESULST"); //print results
//print loanAmount
System.out.println("Loan Amount: " + currency.format(loanAmount));
//print interestRate
System.out.println("Yearly interest rate: " + percent.format(interestRate));
System.out.println("Number of years: " + years); //print years
//print monthlyPayment
System.out.println("Monthly payment: " + currency.format(monthlyPayment));
boolean quit = false;
do {
System.out.println();
System.out.println("Continue? (y/n): "); //prompt user to continue
String userinput1 = sc.next();
char choice1 = userinput1.toLowerCase().charAt(0);
switch (choice1) {
case 'y':
break;
case 'n':
// case n, do something here
quit = true;
break;
case ' ':
System.out.println("Error! This entry is required. Try again.");
break;
default:
System.out.println("Error! Entry must be 'y or 'n''");
break;
}
} while (!quit);
}
}
}
【问题讨论】：
-
“我已经创建了检查范围内数字的方法”：这真的没有太大区别。
-
打印提示后，您需要在应用扫描仪之前阅读用户输入。类似于： String line = new BufferedReader(new InputStreamReader(System.in)).readLine();然后您可以验证 line: if ("Y".equalsIgnoreCase(line)) ....
标签： java string validation