从文件扫描时出现 InputMismatchException

Question

我正在编写一个程序，从输入文件中获取信息（名字和姓氏、小时费率和工作时间）计算净工资并将其写入不同的文件。文件 wages.txt 具有以下内容：

First Name, Last Name, Hourly pay, Hours Worked
Bruce, Wayne, 7.25, 40
John, Jones, 8.50, 45
Clark, Kent, 7.25, 42

输出应该是：

Last Name, First Name, Total Pay
Wayne, Bruce, 290
Jones, John, 361.25
Kent, Clark, 297.25

加班费是时薪的一半。费率是双倍的，工作时间是整数。在我的测试中，输出格式行被写入文件，当程序收集计算工资的信息时抛出异常。

static void wages(){
    //input file
    String file_name = "wages.txt";
    File input_file = new File(file_name);
    Scanner in_file = null;

    //This is the format line that will be wrote to the output file
    String out_format_line = "Last Name, First Name, Total Amount";

    //output file
    String file2_name = "out.txt";
    File output_file = new File(file2_name);
    PrintWriter out_file = null;

    try{
        out_file = new PrintWriter(output_file);
    }
    catch(FileNotFoundException ex){
        System.out.println("Error: The output file does not exist");
        ex.printStackTrace();
        System.exit(0);
    }
    try{
        in_file = new Scanner(input_file);
        in_file.useDelimiter("[,\n]\\s");
    }
    catch(FileNotFoundException ex){
        System.out.println("Error: The input file does not exist");
        ex.printStackTrace();
        System.exit(0);
    }
    try{
        //This line is useless and is removed with this variable
        String in_format_line = in_file.nextLine();
        //writes format line for output file
        out_file.print(out_format_line);
        while(in_file.hasNextLine()){
            //gathers relavent materials for calulating pay
            String first_name = in_file.next();
            String last_name = in_file.next();
            double rate = in_file.nextDouble();
            double over_rate = rate/2;
            int hours = in_file.nextInt();

            //calculates net pay with overtime
            if(hours > 40){
                int overtime = hours - 40;

                double norm_pay = 40*rate;
                double over_pay = overtime * over_rate;

                double net_pay = norm_pay + over_pay;

                out_file.print(last_name);
                out_file.print(", ");
                out_file.print(first_name);
                out_file.print(", ");
                out_file.println(net_pay);
            }
            //calculates net pay without overtime
            else{
                double net_pay = hours*rate;

                out_file.print(last_name);
                out_file.print(", ");
                out_file.print(first_name);
                out_file.print(", ");
                out_file.println(net_pay);
            }
        }
    }
    catch(InputMismatchException ex){
        System.out.println("Error: File format is incorrect");
        ex.printStackTrace();
    }
    finally{
        in_file.close();
        out_file.close();
    }
}

}

当 ex.printStackTrace() 为运行时，控制台显示：

java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:864)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextDouble(Scanner.java:2413)
at guided.exercise.pkg4.GuidedExercise4.wages(GuidedExercise4.java:120)
at guided.exercise.pkg4.GuidedExercise4.main(GuidedExercise4.java:18)

Answer 1

问题出在分隔符上。感谢 Vince Emigh 的建议，他向我展示了我只为换行符和逗号设置了它。因此，当程序扫描输入文件时，它在 290 标记后面包含空格，从而抛出 InputMistmatchException。通过将 in_file.useDelimiter("[,\n]"); 更改为 in_file.useDelimiter("[,\n]\\s"); 它纠正了我遇到的问题。

从文件扫描时出现 InputMismatchException

InputMismatchException when scanning from a file

java

java.util.scanner

java-io