Question

如果输入错误，我不知道如何重新启动程序。

我是Java新手，不知道如何有效地使用if语句或循环。

import java.util.Scanner; 

public class TuitionRates 
{
public static void main(String[] args) 
{
    //variables
    String name = "";
    String studentType = "";
    int creditNumber = 0;
    double totalTF = 0.00;
    double studentACTFee = 4.60;
    double parkingFee = 2.00;
    double tuition = 180.40;
    double capitalFee1 = 0.00;
    double capitalFee2 = 21.00;
    double perCreditR = 187.00;
    double perCreditV = 187.00;
    double perCreditD = 187.00;
    double perCreditM = 208.00;
    double perCreditB = 268.00;
    double perCreditO = 387.25;

    Scanner input = new Scanner(System.in);

    //Asking user for Name
System.out.println("Welcome to the NOVA Tuition and Fees Calculator.");
System.out.println("Please enter your name: ");
name= input.nextLine();

//Ask user to choose option

    System.out.println("Please enter the type of student that your are from 
    the choices below:\n"
            + 
            "R for Virginia Resident\r\n" + 
            "M for Military Contract Out-of-State\r\n" + 
            "V for Military Veterans and Dependents\r\n" + 
            "D for Dual Enrolled\r\n" + 
            "B for Business Contract Students\r\n" + 
            "O for Out of State Students\r\n");

    studentType = input.nextLine();
if (studentType.equalsIgnoreCase("R"))
   {

   System.out.println("Please enter the number of credits that you are 
   taking:");
   creditNumber = input.nextInt();

if (creditNumber <= 18)
{
System.out.println("Tuition and fees report for " + name);          
System.out.println("Tuition: "+ tuition);           
System.out.println( "Capital Fee:  \t"+ capitalFee1);           
System.out.println( "Student Activities Fee: \t "+   studentACTFee);            
System.out.println( "Parking Infrastructure Fee: \t " +  parkingFee);           
System.out.println("Tuition & Fees Per Credit: " +  perCreditR);            
System.out.println("X Number of Credits: " + creditNumber);
totalTF = creditNumber * perCreditR;            
System.out.println("Total Tuition and Fees: \t" +  totalTF);
System.out.println("Bodly NOVA");
}

else {System.out.println("Please re-enter credit Number ");}
}

如果积分超过18，我希望程序重新启动if语句。因此，如果输入19，它将说重新输入积分并开始if结束。

Answer 1

您可以尝试将if语句包装在do-while循环中：

if (studentType.equalsIgnoreCase("R"))
{
    do{
       System.out.println("Please enter the number of credits that you are taking:");
       creditNumber = input.nextInt();

        if (creditNumber <= 18)
        {
            System.out.println("Tuition and fees report for " + name);          
            System.out.println("Tuition: "+ tuition);           
            System.out.println( "Capital Fee:  \t"+ capitalFee1);           
            System.out.println( "Student Activities Fee: \t "+   studentACTFee);            
            System.out.println( "Parking Infrastructure Fee: \t " +  parkingFee);           
            System.out.println("Tuition & Fees Per Credit: " +  perCreditR);            
            System.out.println("X Number of Credits: " + creditNumber);
            totalTF = creditNumber * perCreditR;            
            System.out.println("Total Tuition and Fees: \t" +  totalTF);
            System.out.println("Bodly NOVA");
        }
        else {System.out.println("Please re-enter credit Number ");}
    }while(creditNumber > 18);
}

Answer 2

do-while的构造在这里可能有效。

if (studentType.equalsIgnoreCase("R"))
   {

   do {
       System.out.println("Please enter the number of credits that you are 
       taking:");
       creditNumber = input.nextInt();
       if(creditNumber > 18) System.out.println("Too many credits");
   while(creditNumber > 18);
}

Answer 3

我会做这样的事情：

if (studentType.equalsIgnoreCase("R"))
{

System.out.println("Please enter the number of credits that you are 
taking:");
creditNumber = input.nextInt();

while(creditNumber > 18)
{
    System.out.println("Please re-enter the number of credits that you are 
    taking:");
    creditNumber = input.nextInt();
}

System.out.println("Tuition and fees report for " + name);          
System.out.println("Tuition: "+ tuition);           
System.out.println( "Capital Fee:  \t"+ capitalFee1);           
System.out.println( "Student Activities Fee: \t "+   studentACTFee);            
System.out.println( "Parking Infrastructure Fee: \t " +  parkingFee);           
System.out.println("Tuition & Fees Per Credit: " +  perCreditR);            
System.out.println("X Number of Credits: " + creditNumber);
totalTF = creditNumber * perCreditR;            
System.out.println("Total Tuition and Fees: \t" +  totalTF);
System.out.println("Bodly NOVA");
}

这使用while（）语句检查初始creditNumber是否大于18，并不断提示用户输入新输入。然后，一旦它们提供的值小于或等于18，它就会执行您希望它执行的所有其他操作。请注意，我没有对此进行测试，但是应该可以。

Answer 4

好吧，我可以建议您重新考虑设计。但这不是你的问题-对吗？因此，如果您确实想要，您想要的就是中断（“可怜的人例外”）：

exitpoint:{

     //your code ...
     break exitpoint;
     //more code
     break exitpoint;
     //....
}

或带有某些循环：

exitpoint:
while( ){
    // code....
    for(;;){
        //...
        break exitpoint;
    }
}

处理错误（例如错误的用户输入）的一种更好的方法是例外。但这也不是问题-是吗？

尝试循环到程序开头

4 个答案: