Java while循环工作时出现问题，if语句读取负双精度

我试图为我的java类编写的一些简单代码有两个问题。对不起，如果你们大多数人觉得这很容易，我只是从Java开始。我遇到的第一个问题是循环无法正常继续。它只运行一次就可以了，如果在开始时输入“quit”，它将退出，但在运行一次之后，它不会让用户为emp name输入另一个值。它直接从最后一行输入emp名称到循环的第一行，输入小时费率，没有机会输入新名称或退出

我的第二个问题是我的if语句试图确保为小时工资和工作小时输入的值大于0。如果输入0，则会显示错误消息，但如果输入负数，则程序会继续运行，就像没有任何错误一样。如何确保输入的值仅为正双精度，并且不接受负双精度或零

// Program to Calculate Payroll
import java.util.Scanner;
import java.text.DecimalFormat;

class Payroll
{
   public static void main(String args[])
   {
   Scanner myScanner = new Scanner(System.in);
   String empName;
   double hourlyRate;
   double hoursWorked;
   double grossPay;
   double netPay;
   double taxes;
   DecimalFormat money = new DecimalFormat("$.00");
//Get User Information
   System.out.print( "Enter employee name or enter 'quit' when finished. " );
   empName = myScanner.nextLine();
   while (!empName.equals("quit"))
   {
     System.out.print( "What is their hourly rate? $");
     hourlyRate = myScanner.nextDouble();
     if (hourlyRate <= 0)
     {
         System.out.println( "Value is not valid, please enter an amount above zero.");
         System.out.print( "What is their hourly rate? $");
         hourlyRate = myScanner.nextDouble();
     }
     System.out.print( "How many hours did they work? ");
     hoursWorked = myScanner.nextDouble();
     if (hoursWorked <= 0)
     {
         System.out.println( "Value is not valid, please enter an amount above zero.");
         System.out.print( "How many hours did they work? ");
         hoursWorked = myScanner.nextDouble();
     }
//Calculate Pay and Taxes
     grossPay = hourlyRate * hoursWorked;
     taxes = .13 * grossPay;
     netPay = grossPay - taxes;
//Display All Information
     System.out.print( "Employee name: ");
     System.out.println(empName);
     System.out.print( "Hourly Rate: ");
     System.out.println(money.format(hourlyRate));
     System.out.print( "Hours Worked: ");
     System.out.println(hoursWorked);
     System.out.print( "Gross Pay = ");
     System.out.println(money.format(grossPay));
     System.out.print( "Federal Taxes = ");
     System.out.println(money.format(taxes));
     System.out.print( "Net Pay = ");
     System.out.println(money.format(netPay));
     System.out.print( "Enter employee name or enter 'quit' when finished. " );
     empName = myScanner.nextLine();
   }
   System.out.println( "Thank you for using this payroll program.");
   }
}

//计算工资单的程序
导入java.util.Scanner；
导入java.text.DecimalFormat；
班级工资单
{
公共静态void main（字符串参数[]）
{
Scanner myScanner=新扫描仪（System.in）；
字符串名称；
双钟头；
工作两小时；
重瓣罗缎；
双网支付；
双重征税；
十进制货币=新的十进制货币（$0.00）；
//获取用户信息
系统输出打印（“输入员工姓名或完成后输入“退出”）；
empName=myScanner.nextLine（）；
而（！empName.equals（“退出”））
{
System.out.print（“他们的小时费率是多少？$”）；
hourlyRate=myScanner.nextDouble（）；
如果（hourlyRate作为对第一个问题的响应，您不是在
while
循环中询问员工姓名。您应该在循环外初始化
empName
，但也应该在每次循环时再次询问

String empName = "";
while (!empName.equals("quit")) {
  //Get User Information  
  System.out.print( "Enter employee name or enter 'quit' when finished. " );
  empName = myScanner.nextLine();

  if (empName.equals("quit")) {
    break;
  }

对于第二个问题，您可以再次使用
while
循环并检查以确保
hourlyRate
大于
0
。只要确保每次循环检查时都重新提示即可

hourlyRate = -1;
while (hourlyRate <= 0) {
  System.out.print( "What is their hourly rate? $");
  hourlyRate = myScanner.nextDouble();
  if (hourlyRate <= 0) {
    System.out.println( "Value is not valid, please enter an amount above zero.");
  }
}

hourlyRate=-1；
while（hourlyRate）
它不允许用户为emp名称输入其他值

您只要求输入一次员工姓名，因为它不在循环中。移动代码以在循环中输入姓名。将代码添加到循环的末尾可能会被罚款，但我更喜欢在开始时进行一次检查，中途中断

如何确保输入的值仅为正双精度，并且不接受负双精度或零

// Program to Calculate Payroll
import java.util.Scanner;
import java.text.DecimalFormat;

class Payroll
{
   public static void main(String args[])
   {
   Scanner myScanner = new Scanner(System.in);
   String empName;
   double hourlyRate;
   double hoursWorked;
   double grossPay;
   double netPay;
   double taxes;
   DecimalFormat money = new DecimalFormat("$.00");
//Get User Information
   System.out.print( "Enter employee name or enter 'quit' when finished. " );
   empName = myScanner.nextLine();
   while (!empName.equals("quit"))
   {
     System.out.print( "What is their hourly rate? $");
     hourlyRate = myScanner.nextDouble();
     if (hourlyRate <= 0)
     {
         System.out.println( "Value is not valid, please enter an amount above zero.");
         System.out.print( "What is their hourly rate? $");
         hourlyRate = myScanner.nextDouble();
     }
     System.out.print( "How many hours did they work? ");
     hoursWorked = myScanner.nextDouble();
     if (hoursWorked <= 0)
     {
         System.out.println( "Value is not valid, please enter an amount above zero.");
         System.out.print( "How many hours did they work? ");
         hoursWorked = myScanner.nextDouble();
     }
//Calculate Pay and Taxes
     grossPay = hourlyRate * hoursWorked;
     taxes = .13 * grossPay;
     netPay = grossPay - taxes;
//Display All Information
     System.out.print( "Employee name: ");
     System.out.println(empName);
     System.out.print( "Hourly Rate: ");
     System.out.println(money.format(hourlyRate));
     System.out.print( "Hours Worked: ");
     System.out.println(hoursWorked);
     System.out.print( "Gross Pay = ");
     System.out.println(money.format(grossPay));
     System.out.print( "Federal Taxes = ");
     System.out.println(money.format(taxes));
     System.out.print( "Net Pay = ");
     System.out.println(money.format(netPay));
     System.out.print( "Enter employee name or enter 'quit' when finished. " );
     empName = myScanner.nextLine();
   }
   System.out.println( "Thank you for using this payroll program.");
   }
}

您只要求用户更正数字一次。如果您使用while循环，它将一直询问，直到正确的速率

它不允许用户为emp名称输入其他值

因为你的线路有问题

 hoursWorked = myScanner.nextDouble();

 empName = myScanner.nextLine();

因为这只接受双精度值，而不接受
\n
值。所以，在最后，当程序移动到行时

 hoursWorked = myScanner.nextDouble();

 empName = myScanner.nextLine();

它将继续使用
\n
作为empName，并跳过键盘上的输入
在请求输入empName值之前，需要放置另一个myScanner.nextLine（）

 myScanner.nextLine();
 System.out.println("....");
 empName = myScanner.nextLine();

对于验证，只需像另一个建议的那样执行
循环的末尾确实会再次请求empName，但当我按原样运行时，它会跳过获取该输入，直接返回到循环的顶部。如果我删除循环末尾再次请求信息的最后一行，并将其更改为您建议的方式，则循环将运行一次然后不要重复第一个问题，再问一次名字。