Java读取显示器数据文件出现Scanner输入不匹配错误怎么解决

问题说明 #

现有程序读取显示器参数数据文件时抛出java.util.Scanner相关的InputMismatchException异常，错误栈指向com.company.MonitorsTest.loadMonitors方法，需要定位错误原因并确认数据文件配置是否正确。
数据文件存储字段包含：显示器品牌、型号、刷新率、响应时间。

相关代码 #

class Monitors{
    public String brandName;
    public int modelNumber;
    public int refreshRate;
    public int responseTime;
}
public class MonitorsTest {
    public static void main(String[] args)   {
        Monitors[] gaming = new Monitors[100];
        int dataFile;
        int choice;
        System.out.println("\nDisplay  Monitors\n");
        System.out.println(" Enter one of the following commands:");
        System.out.println("(1)- Display the entire data file ");
        System.out.println("(2) - Display certain information on a monitor");
        System.out.println("(3) - Display a histogram");
        Scanner keyboard = new Scanner(System.in);
        System.out.println();
        System.out.println("Enter 1,  2,  or 3  ");
        choice = keyboard.nextInt();
        dataFile = (loadMonitors(gaming));
        while ( choice != 3){
            if (choice < 1 || choice > 3) {
                System.out.println("Enter 1,  2,  3  ");
                choice = keyboard.nextInt();
            }
            else if (choice == 1){
                System.out.println(dataFile);
            }
        }
    }
    private static int loadMonitors(Monitors[] gaming)  {
        int nMonitors = 0;
        try {
            File file = new File("C:\\Users\\kento\\IdeaProjects\\Program3\\src\\monitors.txt");
            Scanner scan = new Scanner(file);
            do {
                gaming[nMonitors] = new Monitors();
                gaming[nMonitors].brandName = scan.next();
                gaming[nMonitors].modelNumber = scan.next();
                gaming[nMonitors].responseTime = scan.nextDouble();
                gaming[nMonitors].refreshRate = scan.nextInt();
                ++nMonitors;
            }
            while (gaming[nMonitors - 1].refreshRate != 0);
            --nMonitors;
        }
        catch (IOException ioe){
            System.out.println(" File access error" + ioe);
            nMonitors = 0;
        }
        return nMonitors;
    }
}

错误日志 #

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:864)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at com.company.MonitorsTest.loadMonitors(MonitorsTest.java:62)
at com.company.MonitorsTest.main(MonitorsTest.java:39)

数据文件内容 #

Sceptre DCIP3       1       165
AOC     C24G1A      1       165
ASUS    VG278QR     05      144
Sceptre E22          5      75
Alienware   AW2521HF 1      240

错误根因 #

• 字段类型不匹配：Monitors类中modelNumber定义为int类型，但实际数据文件中的型号值（如DCIP3、C24G1A）包含字母，无法转换为整数，直接触发类型转换异常。
• 读取方法和类型不对应：代码中给modelNumber赋值时调用的是scan.next()，返回的是String类型，直接赋值给int变量本身就会报错；同时responseTime定义为int类型，但代码调用了scan.nextDouble()读取，类型不匹配。
• 循环终止条件错误：现有循环终止的判断条件是读取到的refreshRate等于0，但提供的数据文件中没有refreshRate为0的行，读完所有文件内容后再调用读取方法会直接抛出异常。

修复方案 #

1. 调整Monitors类的字段类型，将modelNumber改为String类型适配带字母的型号数据。
2. 修正读取逻辑的类型和顺序，适配数据文件的字段规则：

// 数据每行的字段顺序为：品牌、型号、响应时间、刷新率，全部对应类型读取
gaming[nMonitors].brandName = scan.next();
gaming[nMonitors].modelNumber = scan.next();
gaming[nMonitors].responseTime = scan.nextInt();
gaming[nMonitors].refreshRate = scan.nextInt();

3. 调整循环读取逻辑，优先判断是否还有未读取的内容，避免读完文件后继续读取：

// 替换原有的do-while循环
while (scan.hasNext()) {
    gaming[nMonitors] = new Monitors();
    gaming[nMonitors].brandName = scan.next();
    gaming[nMonitors].modelNumber = scan.next();
    gaming[nMonitors].responseTime = scan.nextInt();
    gaming[nMonitors].refreshRate = scan.nextInt();
    ++nMonitors;
    // 如果要保留原有refreshRate=0终止的逻辑，可在这里加判断
    if (gaming[nMonitors - 1].refreshRate == 0) {
        --nMonitors;
        break;
    }
}

4. 读取完成后调用scan.close()释放Scanner资源。
5. 数据文件无需调整，现有格式符合空白符分割的读取规则。

内容的提问来源于stack exchange，提问作者SimplyKenton