是什么导致了"Exception in thread "主" java.util.InputMismatchException"错误？

Question

要开始我的问题，下面是我的问题提示：

Create a program using classes that does the following in the zyLabs developer below. For this lab, you will be working with two different class files. To switch files, look for where it says "Current File" at the top of the developer window. Click the current file name, then select the file you need.
(1) Create two files to submit:
ItemToPurchase.java - Class definition
ShoppingCartPrinter.java - Contains main() method
Build the ItemToPurchase class with the following specifications:
Private fields
String itemName - Initialized in default constructor to "none"
int itemPrice - Initialized in default constructor to 0
int itemQuantity - Initialized in default constructor to 0
Default constructor
Public member methods (mutators & accessors)
setName() & getName() (2 pts)
setPrice() & getPrice() (2 pts)
setQuantity() & getQuantity() (2 pts)
(2) In main(), prompt the user for two items and create two objects of the ItemToPurchase class. Before prompting for the second item, call scnr.nextLine(); to allow the user to input a new string. (2 pts)
Ex:
Item 1
Enter the item name: Chocolate Chips
Enter the item price: 3
Enter the item quantity: 1
Item 2
Enter the item name: Bottled Water
Enter the item price: 1
Enter the item quantity: 10
(3) Add the costs of the two items together and output the total cost. (2 pts)
Ex:
TOTAL COST
Chocolate Chips 1 @ $3 = $3
Bottled Water 10 @ $1 = $10
Total: $13  

我的代码：

ItemToPurhase.java

public class ItemToPurchase {
//Private fields - itemName, itemPrice, and itemQuanity
private String itemName = "none";
private int itemPrice = 0;
private int itemQuantity = 0;
/*Default Constructor
itemName - Initialized to "none"
itemPrice - Initialized to 0
itemQuantity - Initialized ito 0
*/

public ItemToPurchase () {
this.itemName = "none";
this.itemPrice = 0;
this.itemQuantity = 0;
}   

//public member methods (mutators & accessors)

//setName() & getName() 
public void setName (String itemName) {
this.itemName = itemName;
}

public String getName() {
return itemName;
}

//setPrice() & getPrice() 
public void setPrice (int itemPrice) {
this.itemPrice = itemPrice;
}

public int getPrice(){
return itemPrice;
}

//setQuantity() & getQuantity() 
public void setQuantity (int itemQuantity) {
this.itemQuantity = itemQuantity;
}

public int getQuantity() {
return itemQuantity;
}

//print item to purchase

public void printItemPurchase() {
System.out.println(itemQuantity + " " + itemName + " $" + itemPrice +  
" = $" + (itemPrice * itemQuantity));
}
}

ShoppingCartPrinter.java

import java.util.Scanner;
public class ShoppingCartPrinter {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
int i = 0;
String productName;
int productPrice = 0;
int productQuantity = 0;
int cartTotal = 0;

ItemToPurchase item1 = new ItemToPurchase();
ItemToPurchase item2 = new ItemToPurchase();
// Get item 1 details from user, create itemToPurchase object
System.out.println("Item 1");

System.out.println("Enter the item name: ");
productName = scnr.next();
item1.setName(productName);

System.out.println("Enter the item price: ");
productPrice = scnr.nextInt();
item1.setPrice(productPrice);

System.out.println("Enter the item quantity: ");
productQuantity = scnr.nextInt();
item1.setQuantity(productQuantity);

System.out.println("");

// Get item 2 details from user, create itemToPurchase object
System.out.println("Item 2");

System.out.println("Enter the item name: ");
productName = scnr.next();
item2.setName(productName);

System.out.println("Enter the item price: ");
productPrice = scnr.nextInt();
item2.setPrice(productPrice);

System.out.println("Enter the item quantity: ");
productQuantity = scnr.nextInt();
item2.setQuantity(productQuantity);

System.out.println("");


// Add costs of two items and print total
cartTotal = (item1.getQuantity() * item1.getPrice()) + (item2.getQuantity() * item2.getPrice());
System.out.println("TOTAL COST");
// cartTotal = item one price + item two price
// Totoal Cost
// item one information
int item1Total = item1.getPrice() * item1.getQuantity();
System.out.println(item1.getName() + " " + item1.getQuantity() +  " @ $" + item1.getPrice() + " = $" + item1Total);
// item two information
int item2Total = item2.getPrice() * item2.getQuantity();
System.out.println(item2.getName() + " " + item2.getQuantity() +  " @ $" + item2.getPrice() + " = $" + item2Total);
// Total output
System.out.println("");
System.out.print("Total: $" + cartTotal);
return;
}

}

尽管我在大多数提交的材料中没有错误，但有2份提交的材料提出了"；线程中的异常"；主"；java.util.InputMismatchException"错误

示例：

Exited with return code 1.  
Exception in thread "main" java.util.InputMismatchException  
at java.base/java.util.Scanner.throwFor(Scanner.java:939)  
at java.base/java.util.Scanner.next(Scanner.java:1594)  
at java.base/java.util.Scanner.nextInt(Scanner.java:2258)  
at java.base/java.util.Scanner.nextInt(Scanner.java:2212)  
at ShoppingCartPrinter.main(ShoppingCartPrinter.java:23)

Output differs. See highlights below. 
Input:
Chocolate Chips
3
1
Bottled Water
1
10
Your output:
Item 1
Enter the item name: 
Enter the item price: 
Expected output(!):
Item 1
Enter the item name: 
Enter the item price: 
Enter the item quantity: 
Item 2
Enter the item name: 
Enter the item price: 
Enter the item quantity: 
TOTAL COST
Chocolate Chips 1 @ $3 = $3
Bottled Water 10 @ $1 = $10
Total: $13

对于其他非常相似的输入，我的代码似乎是正确的，但出于某种原因，我的教授使用的编译器在极少数情况下不断提示这个错误。

Answer 1

如果您还没有这样做，我建议您阅读java.util.Scanner.类的文档

您的这一行代码正在抛出InputMismatchException。

productPrice = scnr.nextInt();

这意味着scnr读取的令牌不是int。这是因为您的产品包含两个单词，即巧克力片。所以这行代码只读巧克力

productName = scnr.next();

因此方法CCD_ 4读取不是CCD_ 5的芯片。

您需要更改代码并调用方法nextLine，而不是方法next。再次，请参阅文档以了解原因。

此外，在调用方法nextInt之后和调用方法nextLine之前，您需要对方法nextLine进行额外的调用。请参阅扫描仪在使用next((或nextFo((后是否跳过nextLine((？了解原因。

只有类别ShoppingCartPrinter需要更改。这是更改后的代码。我添加了注释来指示更改，即CHANGE HERE和ADDED THIS LINE。

import java.util.Scanner;
public class ShoppingCartPrinter {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
int i = 0;
String productName;
int productPrice = 0;
int productQuantity = 0;
int cartTotal = 0;
ItemToPurchase item1 = new ItemToPurchase();
ItemToPurchase item2 = new ItemToPurchase();
// Get item 1 details from user, create itemToPurchase object
System.out.println("Item 1");
System.out.println("Enter the item name: ");
productName = scnr.nextLine(); // CHANGE HERE
item1.setName(productName);
System.out.println("Enter the item price: ");
productPrice = scnr.nextInt();
item1.setPrice(productPrice);
System.out.println("Enter the item quantity: ");
productQuantity = scnr.nextInt();
item1.setQuantity(productQuantity);
scnr.nextLine(); // ADDED THIS LINE
System.out.println("");
// Get item 2 details from user, create itemToPurchase object
System.out.println("Item 2");
System.out.println("Enter the item name: ");
productName = scnr.nextLine(); // CHANGE HERE
item2.setName(productName);
System.out.println("Enter the item price: ");
productPrice = scnr.nextInt();
item2.setPrice(productPrice);
System.out.println("Enter the item quantity: ");
productQuantity = scnr.nextInt();
item2.setQuantity(productQuantity);
System.out.println("");
// Add costs of two items and print total
cartTotal = (item1.getQuantity() * item1.getPrice())
+ (item2.getQuantity() * item2.getPrice());
System.out.println("TOTAL COST");
// cartTotal = item one price + item two price
// Totoal Cost
// item one information
int item1Total = item1.getPrice() * item1.getQuantity();
System.out.println(item1.getName() + " " + item1.getQuantity() + " @ $" + item1.getPrice()
+ " = $" + item1Total);
// item two information
int item2Total = item2.getPrice() * item2.getQuantity();
System.out.println(item2.getName() + " " + item2.getQuantity() + " @ $" + item2.getPrice()
+ " = $" + item2Total);
// Total output
System.out.println("");
System.out.print("Total: $" + cartTotal);
return;
}
}