Java 如何捕获hasNextInt（）字符串输入异常？
在我的java应用程序（一个简单的TollMachine模拟器）中，我必须在代码中实现try/catch代码。我设法在hasNextInt提示符下处理字符串输入，但是当我尝试使用try/catch执行相同的操作时，我无法让程序进入catch部分。程序进入无限循环，我真的需要让它使用try/catch方法。否则，我使用if（hasNextInt）/else（变通方法）来摆脱字符串输入并防止无限循环Java 如何捕获hasNextInt（）字符串输入异常？,java,exception,exception-handling,try-catch,Java,Exception,Exception Handling,Try Catch,在我的java应用程序（一个简单的TollMachine模拟器）中，我必须在代码中实现try/catch代码。我设法在hasNextInt提示符下处理字符串输入，但是当我尝试使用try/catch执行相同的操作时，我无法让程序进入catch部分。程序进入无限循环，我真的需要让它使用try/catch方法。否则，我使用if（hasNextInt）/else（变通方法）来摆脱字符串输入并防止无限循环 public class TollMachine { static boolean run
public class TollMachine {
static boolean running = true; //variable to control whether the program should run
static int userInput = -1; //variable to store the user's input
static String userInput2 = ""; //variable to store the input in case user does not enter an integer
static int motoTicketCount = 0; //variable to store the number of tickets sold(moto)
static int carTicketCount = 0; //variable to store the number of tickets sold(car)
static int vanTicketCount = 0; //variable to store the number of tickets sold(van)
static int truckTicketCount = 0;//variable to store the number of tickets sold(truck)
static int totalTicketCount = 0;//variable to store the number of total tickets sold
static Scanner keyb = new Scanner(System.in); //variable to detect the user's input
public static void main(String[] args) {
while (userInput != 0) //runs while userInput != 0
{
//This is the main menu, the user is prompted to choose an option
System.out.println("1. Motorcycle");
System.out.println("2. Car");
System.out.println("3. Van");
System.out.println("4. Truck");
System.out.println("5. Display total tickets sold.");
System.out.println("0. Exit");
try {
if (keyb.hasNextInt()) //checks whether the user inputs an integer
{
userInput = keyb.nextInt(); //stores the user's input to the userInput
if (userInput > 5 || userInput < 0) //if one of these conditions are true, the user selected an option
{ //that is not mentioned
System.out.println("Invalid input."); //displays the Invalid input error
} else {
//checks which option the user chose with multiple "if" conditions
if (userInput == 1) {
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your motorcycle ticket.");
motoTicketCount++;
totalTicketCount++;
}
if (userInput == 2) {
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your car ticket.");
carTicketCount++;
totalTicketCount++;
}
if (userInput == 3) {
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your van ticket.");
vanTicketCount++;
totalTicketCount++;
}
if (userInput == 4) {
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your truck ticket.");
truckTicketCount++;
totalTicketCount++;
}
if (userInput == 5) {
//Displays how many of each ticket were sold, and the total number of tickets sold
System.out.println("Motorcycle tickets sold: " + motoTicketCount);
System.out.println("Car tickets sold: " + carTicketCount);
System.out.println("Van tickets sold: " + vanTicketCount);
System.out.println("Truck tickets sold: " + truckTicketCount);
System.out.println("Total tickets sold: " + totalTicketCount);
}
if (userInput == 0) {
running = false; //terminates the program
}
}//end of else after the if (hasNextInt())
}//end of first if (hasNextInt())
}//end of try
catch (Exception e) //this SHOULD catch an invalid input error
{
System.out.println("Invalid input."); //displays invalid input in case the
userInput2 = keyb.next(); //discard the bad input
}
}
}
}
公共类收费机{
static boolean running=true；//用于控制程序是否应运行的变量
static int userInput=-1；//用于存储用户输入的变量
静态字符串userInput2=“”；//在用户未输入整数的情况下存储输入的变量
static int motoTicketCount=0；//用于存储已售出票数（moto）的变量
static int carTicketCount=0；//用于存储售出车票数量（车）的变量
static int vanTicketCount=0；//用于存储已售出车票（van）数量的变量
静态int-truckTicketCount=0；//用于存储已售出车票数量（卡车）的变量
静态int totalTicketCount=0；//用于存储已售出总票数的变量
static Scanner keyb=new Scanner（System.in）；//用于检测用户输入的变量
公共静态void main（字符串[]args）{
while（userInput！=0）//在userInput！=0时运行
{
//这是主菜单，提示用户选择一个选项
系统输出打印（“1.摩托车”）；
System.out.println（“2.Car”）；
System.out.println（“3.Van”）；
系统输出打印（“4.卡车”）；
System.out.println（“5.显示售出的总票数”）；
System.out.println（“0.Exit”）；
试一试{
if（keyb.hasNextInt（））//检查用户是否输入整数
{
userInput=keyb.nextInt（）；//将用户的输入存储到userInput
if（userInput>5 | | userInput<0）//如果这些条件之一为真，则用户选择了一个选项
{//没有提到这一点
System.out.println（“无效输入”）；//显示无效输入错误
}否则{
//使用多个“如果”条件检查用户选择的选项
if（userInput==1）{
//向用户显示适当的消息，并将两个计数器增加1
System.out.println（“这是你的摩托车票。”）；
motoTicketCount++；
totalTicketCount++；
}
if（userInput==2）{
//向用户显示适当的消息，并将两个计数器增加1
System.out.println（“这是你的车票。”）；
carTicketCount++；
totalTicketCount++；
}
if（userInput==3）{
//向用户显示适当的消息，并将两个计数器增加1
System.out.println（“这是你的货车票。”）；
vanTicketCount++；
totalTicketCount++；
}
if（userInput==4）{
//向用户显示适当的消息，并将两个计数器增加1
System.out.println（“这是你的卡车票。”）；
truckTicketCount++；
totalTicketCount++；
}
if（userInput==5）{
//显示每张票的售出数量以及售出的总票数
System.out.println（“摩托车票售出：+motoTicketCount”）；
System.out.println（“售出车票：+carTicketCount”）；
System.out.println（“售出的客票：+vanTicketCount”）；
System.out.println（“售出的卡车票：+truckTicketCount”）；
System.out.println（“售出总票数：+totalTicketCount”）；
}
if（userInput==0）{
running=false；//终止程序
}
}//if（hasNextInt（））后面的else结束
}//第一个if的结束（hasNextInt（））
}//尝试结束
catch（异常e）//这应该捕获无效的输入错误
{
System.out.println（“无效输入”）；//在
userInput2=keyb.next（）；//放弃错误的输入
}
}
}
}
if (userInput >5 || userInput<0) //if one of these conditions are true, the user selected an option
{ //that is not mentioned
System.out.println("Invalid input."); //displays the Invalid input error
}
if（keyb.hasNext（））integer.parseInt（keyb.next（））将输入转换为整数并捕获结果NumberFormatException
此外，您可以只设置userInput=-1，而不是使用userInput2
变量来存储错误数据
重新启动catch函数中的循环
完整代码：
public class TollMachine
{
static boolean running = true; //variable to control whether the program should run
static int userInput = -1; //variable to store the user's input
static String userInput2 = ""; //variable to store the input in case user does not enter an integer
static int motoTicketCount = 0; //variable to store the number of tickets sold(moto)
static int carTicketCount = 0; //variable to store the number of tickets sold(car)
static int vanTicketCount = 0; //variable to store the number of tickets sold(van)
static int truckTicketCount = 0;//variable to store the number of tickets sold(truck)
static int totalTicketCount = 0;//variable to store the number of total tickets sold
static Scanner keyb = new Scanner(System.in); //variable to detect the user's input
public static void main(String[] args)
{
while (userInput != 0) //runs while userInput != 0
{
//This is the main menu, the user is prompted to choose an option
System.out.println("1. Motorcycle");
System.out.println("2. Car");
System.out.println("3. Van");
System.out.println("4. Truck");
System.out.println("5. Display total tickets sold.");
System.out.println("0. Exit");
try
{
/**
THIS THROWS YOUR EXCEPTION
**/
if (keyb.hasNext())
{
userInput = Interger.parseInt(keyb.next()); //stores the user's input to the userInput
if (userInput >5 || userInput<0) //if one of these conditions are true, the user selected an option
{ //that is not mentioned
System.out.println("Invalid input."); //displays the Invalid input error
}
else
{
//checks which option the user chose with multiple "if" conditions
if (userInput == 1)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your motorcycle ticket.");
motoTicketCount++;
totalTicketCount++;
}
if (userInput == 2)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your car ticket.");
carTicketCount++;
totalTicketCount++;
}
if (userInput == 3)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your van ticket.");
vanTicketCount++;
totalTicketCount++;
}
if (userInput == 4)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your truck ticket.");
truckTicketCount++;
totalTicketCount++;
}
if (userInput == 5)
{
//Displays how many of each ticket were sold, and the total number of tickets sold
System.out.println("Motorcycle tickets sold: "+motoTicketCount);
System.out.println("Car tickets sold: "+carTicketCount);
System.out.println("Van tickets sold: "+vanTicketCount);
System.out.println("Truck tickets sold: "+truckTicketCount);
System.out.println("Total tickets sold: "+totalTicketCount);
}
if (userInput == 0)
{
running = false; //terminates the program
}
}//end of else after the if (hasNextInt())
}//end of first if (hasNextInt())
}//end of try
catch (NumberFormatException e) //this SHOULD catch an invalid input error
{
System.out.println("Invalid input."); //displays invalid input in case the
userInput = -1;
}
}
}
}
公共类收费机
{
static boolean running=true；//用于控制程序是否应运行的变量
static int userInput=-1；//用于存储用户输入的变量
静态字符串userInput2=“”；//sto的变量
public class TollMachine
{
static boolean running = true; //variable to control whether the program should run
static int userInput = -1; //variable to store the user's input
static String userInput2 = ""; //variable to store the input in case user does not enter an integer
static int motoTicketCount = 0; //variable to store the number of tickets sold(moto)
static int carTicketCount = 0; //variable to store the number of tickets sold(car)
static int vanTicketCount = 0; //variable to store the number of tickets sold(van)
static int truckTicketCount = 0;//variable to store the number of tickets sold(truck)
static int totalTicketCount = 0;//variable to store the number of total tickets sold
static Scanner keyb = new Scanner(System.in); //variable to detect the user's input
public static void main(String[] args)
{
while (userInput != 0) //runs while userInput != 0
{
//This is the main menu, the user is prompted to choose an option
System.out.println("1. Motorcycle");
System.out.println("2. Car");
System.out.println("3. Van");
System.out.println("4. Truck");
System.out.println("5. Display total tickets sold.");
System.out.println("0. Exit");
try
{
/**
THIS THROWS YOUR EXCEPTION
**/
if (keyb.hasNext())
{
userInput = Interger.parseInt(keyb.next()); //stores the user's input to the userInput
if (userInput >5 || userInput<0) //if one of these conditions are true, the user selected an option
{ //that is not mentioned
System.out.println("Invalid input."); //displays the Invalid input error
}
else
{
//checks which option the user chose with multiple "if" conditions
if (userInput == 1)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your motorcycle ticket.");
motoTicketCount++;
totalTicketCount++;
}
if (userInput == 2)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your car ticket.");
carTicketCount++;
totalTicketCount++;
}
if (userInput == 3)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your van ticket.");
vanTicketCount++;
totalTicketCount++;
}
if (userInput == 4)
{
//Displays an appropriate message to the user, and increases the two counters by 1
System.out.println("Here is your truck ticket.");
truckTicketCount++;
totalTicketCount++;
}
if (userInput == 5)
{
//Displays how many of each ticket were sold, and the total number of tickets sold
System.out.println("Motorcycle tickets sold: "+motoTicketCount);
System.out.println("Car tickets sold: "+carTicketCount);
System.out.println("Van tickets sold: "+vanTicketCount);
System.out.println("Truck tickets sold: "+truckTicketCount);
System.out.println("Total tickets sold: "+totalTicketCount);
}
if (userInput == 0)
{
running = false; //terminates the program
}
}//end of else after the if (hasNextInt())
}//end of first if (hasNextInt())
}//end of try
catch (NumberFormatException e) //this SHOULD catch an invalid input error
{
System.out.println("Invalid input."); //displays invalid input in case the
userInput = -1;
}
}
}
}