Java蛋糕工厂程序读取文件时抛出InputMismatchException异常求助

异常现象 #

运行TheCupcakeFactory程序时，输出欢迎消息后抛出InputMismatchException，程序终止执行。异常堆栈信息如下：

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 TheCupcakeFactory.main(TheCupcakeFactory.java:35)

相关代码与文件内容 #

TheCupcakeFactory主类代码 #

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class TheCupcakeFactory 
{
    private static Scanner inputFile;
    /*
     *Diego Molina Salinas
     *CS160 Fall 2023
     *Project 4: The Cupcake Factory Sales
     *
     */
    public static void main(String[] args) throws IOException
    {
        Cupcake cupcakeCS = new Cupcake();
        Cupcake cupcakeAP = new Cupcake();
        Cupcake cupcakeBF = new Cupcake();
        Cupcake cupcakeBS = new Cupcake();
        Cupcake cupcakeBW = new Cupcake();
        
        Cupcake [] cupcakes = {cupcakeCS, cupcakeAP, cupcakeBF, cupcakeBS, cupcakeBW};
        System.out.println("Welcome to the Cupcake Factory Sales Registry!!");
        
        FileReader file = new FileReader("FreshCupcakes.txt");
        inputFile = new Scanner(file);

        //This is setting the Chocolate Strawberry Cupcake
        cupcakeCS.setFlavor(inputFile.next());
        cupcakeCS.setDescription("Moist chocolate cake filled with strawberry jam, topped with strawberry buttercream dipped in chocolate.");
        cupcakeCS.setUnitsOnHand(inputFile.nextInt());
        cupcakeCS.setPrice(2.75);
        //This is setting the Apple Pie Cupcake
        cupcakeAP.setFlavor(inputFile.next());
        cupcakeAP.setDescription("Moist vanilla cake filled with apple pie filling; topped with cream cheese icing, apple pie filling, and cinnamon streusel");
        cupcakeAP.setUnitsOnHand(inputFile.nextInt());
        cupcakeAP.setPrice(3.25);
        //This is setting the Butterfinger Cupcake
        cupcakeBF.setFlavor(inputFile.next());
        cupcakeBF.setDescription("Moist chocolate cake filled and topped with our peanut butter icing and Butterfinger candy.");
        cupcakeBF.setUnitsOnHand(inputFile.nextInt());
        cupcakeBF.setPrice(2.95);
        //This is setting the Banana Split Cupcake
        cupcakeBS.setFlavor(inputFile.next());
        cupcakeBS.setDescription("Moist chocolate cake filled with banana filling, topped with our vanilla buttercream with sprinkles, cherry and chocolate drizzle on top.");
        cupcakeBS.setUnitsOnHand(inputFile.nextInt());
        cupcakeBS.setPrice(3.15);
        //This is setting the Black & White Cupcake
        cupcakeBW.setFlavor(inputFile.next());
        cupcakeBW.setDescription("  Moist vanilla cupcake, topped with our rich fudge icing");
        cupcakeBW.setUnitsOnHand(inputFile.nextInt());
        cupcakeBW.setPrice(3.50);
        for (Cupcake cupcake : cupcakes) {
            System.out.println(cupcake);
        }

    }
}

Cupcake类代码 #

public class Cupcake 
{
String flavor;
String description;
int unitsOnHand;
double price;

public Cupcake() {
    // TODO Auto-generated constructor stub
    this.flavor = "";
    this.description = "";
    this.unitsOnHand = 0;
    this.price = 0.0;
    
}
public String getFlavor() {
    return flavor;
}
public void setFlavor(String flavor) {
    this.flavor = flavor;
}
public String getDescription() {
    return description;
}
public void setDescription(String description) {
    this.description = description;
}
public int getUnitsOnHand() {
    return unitsOnHand;
}
public void setUnitsOnHand(int unitsOnHand) {
    this.unitsOnHand = unitsOnHand;
}
public double getPrice() {
    return price;
}
public void setPrice(double price) {
    this.price = price;
}
public void newUnitsOnHand(int quantity) {
    unitsOnHand = unitsOnHand - quantity;
}
@Override
public String toString() {
     return flavor + ": \t\t $" + price + " - " + description;
}

}

FreshCupcakes.txt文件内容 #

Chocolate Strawberry 25
Apple Pie 15
Butterfinger 25
Banana Split 30
Black & White 50

问题原因 #

代码中使用inputFile.next()读取蛋糕口味，但部分口味由多个单词组成（如Chocolate Strawberry）。Scanner.next()默认以空格为分隔符，只会读取到第一个空格前的内容（比如Chocolate），后续调用inputFile.nextInt()时，读取到的是第二个单词（Strawberry），而非预期的数字，因此抛出InputMismatchException。

解决方案 #

推荐采用按行读取文件的方式，拆分每行内容获取完整口味名称和库存数量，这种方法适配任意单词数的口味名称，鲁棒性更强。

修改主类中的文件读取逻辑如下：

FileReader file = new FileReader("FreshCupcakes.txt");
inputFile = new Scanner(file);

// 按行读取并处理每个蛋糕的信息
int index = 0;
while (inputFile.hasNextLine()) {
    String line = inputFile.nextLine().trim();
    if (line.isEmpty()) continue;
    
    // 拆分每行：最后一个空格前的内容为口味，后面的为库存数量
    int lastSpacePos = line.lastIndexOf(" ");
    String flavor = line.substring(0, lastSpacePos).trim();
    int units = Integer.parseInt(line.substring(lastSpacePos + 1).trim());
    
    cupcakes[index].setFlavor(flavor);
    cupcakes[index].setUnitsOnHand(units);
    index++;
}

// 保持原有的描述和价格设置逻辑
cupcakeCS.setDescription("Moist chocolate cake filled with strawberry jam, topped with strawberry buttercream dipped in chocolate.");
cupcakeCS.setPrice(2.75);
cupcakeAP.setDescription("Moist vanilla cake filled with apple pie filling; topped with cream cheese icing, apple pie filling, and cinnamon streusel");
cupcakeAP.setPrice(3.25);
cupcakeBF.setDescription("Moist chocolate cake filled and topped with our peanut butter icing and Butterfinger candy.");
cupcakeBF.setPrice(2.95);
cupcakeBS.setDescription("Moist chocolate cake filled with banana filling, topped with our vanilla buttercream with sprinkles, cherry and chocolate drizzle on top.");
cupcakeBS.setPrice(3.15);
cupcakeBW.setDescription("  Moist vanilla cupcake, topped with our rich fudge icing");
cupcakeBW.setPrice(3.50);

for (Cupcake cupcake : cupcakes) {
    System.out.println(cupcake);
}

如果不想修改整体逻辑，也可以针对每个多单词口味，手动拼接读取的单词：

// 读取Chocolate Strawberry口味
cupcakeCS.setFlavor(inputFile.next() + " " + inputFile.next());
cupcakeCS.setUnitsOnHand(inputFile.nextInt());

// 读取Apple Pie口味
cupcakeAP.setFlavor(inputFile.next() + " " + inputFile.next());
cupcakeAP.setUnitsOnHand(inputFile.nextInt());

// 其余单单词口味保持原逻辑
cupcakeBF.setFlavor(inputFile.next());
cupcakeBF.setUnitsOnHand(inputFile.nextInt());

但这种方法仅适用于已知口味单词数的场景，扩展性较差。

内容的提问来源于stack exchange，提问作者moemoe