java.lang.NumberFormatException : For input string when using scanner to read the file 异常

Question

我不确定为什么会收到此错误以及在以下代码片段中如何修复它:

        String srcFile=args[0];
        Scanner fileIn = new Scanner(srcFile);
        //    if (fileIn.isFile() && fileIn.canRead())

        CarDB carDatabase = new CarDB();
        while(fileIn.hasNext())
        {       
          String[] line = fileIn.nextLine().split(",");
          double mpg = Double.parseDouble(line[0]);
          int cylinders = Integer.parseInt(line[1]);
          int power = Integer.parseInt(line[2]);
          int year = Integer.parseInt(line[3]);
          int region = Integer.parseInt(line[4]);
          String makerName = line[5].trim();
          String carName = line[6].trim();

          carDatabase.addCar(makerName, carName, mpg, cylinders, power, year, region);// add car
          carDatabase.addMaker(makerName);//add maker to list

        } 

第 36 行是:double mpg = Double.parseDouble(line[0]);

错误是:

java CarDBMain cars.txt 
java.lang.NumberFormatException: For input string: "cars.txt"
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1250)
    at java.lang.Double.parseDouble(Double.java:540)
    at CarDBMain.main(CarDBMain.java:36)

Answer 1

你有这个 Scanner fileIn = new Scanner("cars.txt"); 所以你的第一行将是 "cars.txt"

 Scanner fileIn = new Scanner(new File(srcFile));//Or probably path of file

此处创建文件并将命令行参数(表示文件路径)传递给文件构造函数并将该文件传递给Scanner .

您正在将文件名作为 String 传递给 Scanner。

构造函数

Scanner(File source)<---Takes File you want to read
Scanner(String source)<----Takes String you want to read
etc.