我正在尝试打开我的文本文件，但我不知道问题出在哪里

Question

I am trying to make a program that takes in a students id number, first and last name along with their class grade. After I want to be able to read the data. But I am getting an error when I try to read the data ( or open the file). When I run the program I get "Error opening file". I have 5 classes and will attach them. Could someone try to help me out and find out what is wrong. I will attach the classes:

    public class StudentRecords 
    {
        private int IDnumber;
        private String firstName;
        private String lastName;
        private double grade;

       public StudentRecords()
       {
            this( 0, "", "", 0.0);

        }

        public StudentRecords( int id, String first, String last, double gr )
        {
            setIDnumber( id );
            setFirstName( first);
            setLastName( last );
            setGrade( gr );
        }
        public void setIDnumber( int id)
        {
            IDnumber = id;
        }

        public int getIDnumber()
        {
            return IDnumber;
        }

         public void setFirstName( String first )
        {
            firstName = first;
        }

        public String getFirstName()
        }
            return firstName;
        }

        public void setLastName( String last)
        {
            lastName = last;
        }

        public String getLastName()
        {
            return lastName;
        }

        public void setGrade( double gr)
        {
            grade = gr;
        }

        public double getGrade()
        {
            return grade;

        }
    }

Here is the second class

    import java.io.FileNotFoundException;
    import java.lang.SecurityException;
    import java.util.Formatter;
    import java.util.FormatterClosedException;
    import java.util.NoSuchElementException;
    import java.util.Scanner;

    public class StudentTextFile 
    {
        private Formatter output;

        public void openFile()
        {
            try
            {
                output = new Formatter( "students.txt");
            }
            catch ( SecurityException securityException )
            {
                System.err.println(
                    "You do not have write access to this file.");
                System.exit(1);

            }
            catch ( FileNotFoundException fileNotFoundException )
            {
                System.err.println( "Error opening or creating file." );
                System.exit(1);
            }
        }

        public void addStudentRecords()
        {
            StudentRecords record = new StudentRecords();
            Scanner input = new Scanner( System.in);

            System.out.printf("%s\n%s\n%s\n%s\n\n",
            "To terminate input, type the end-of-file indicator",
            "when you are prompted to enter input.",
            "On UNIX/Linux/Mac OS X type <ctrl> d then press Enter",
            "On Windows type <crtl> z then press enter");

            System.out.printf( "%s\n%s",
        "Enter student ID number (> 0), first name, last name and grade. ",
            "? ");

            while ( input.hasNext() )
            {
                try
                {
                    record.setIDnumber( input.nextInt());
                    record.setFirstName( input.next());
                    record.setLastName(input.next());
                    record.setGrade( input.nextDouble());

               if ( record.getIDnumber() > 0 )
               {
                    output.format( "%d %s %s %.2f\n", record.getIDnumber(),
                    record.getFirstName(), record.getLastName(), 
                record.getGrade() );
                }
                 else
                {
                System.out.println(
                        "Student ID Number must be greater than 0.");
            }
        }
        catch ( FormatterClosedException formatterClosedException)
        {
            System.err.println( "Error writing to file.");
            return;
        }
        catch ( NoSuchElementException elementException)
        {
            System.err.println( "Invalid input. Please try again.");
            input.nextLine();

        }
        System.out.printf( "%s %s \n%s", "Enter student ID number (>0),",
                "first name. last name and grade.", "? ");
    }
}
public void closeFile()
{
    if ( output != null )
        output.close();
}

}

Here is the third class

    public class StudentTextFileTest {

        public static void main(String[] args) 
        {

            StudentTextFile application = new StudentTextFile();

            application.openFile();
            application.addStudentRecords();
            application.closeFile();

        }

    }   

Here is the fourth class

    import java.io.File;
    import java.io.FileNotFoundException;
    import java.lang.IllegalStateException;
    import java.util.NoSuchElementException;
    import java.util.Scanner;

    public class ReadStudentTextFile 
    {
        private Scanner input;

        public void openfile()
        {
            try
            {
                input = new Scanner( new File( "studentrecords.txt"));
            }
            catch ( FileNotFoundException fileNotFoundException )
            {
                System.err.println( "Error opening file.");
                System.exit(1);

            }
        }

        public void readStudentRecords()
        {
            StudentRecords record = new StudentRecords();

            System.out.printf( "%-10s%-12s%-12s%10s\n", "Student ID Number",
            "First Name", "Last Name", "Balance");

        try 
        {
            while ( input.hasNext())
            {
                record.setIDnumber( input.nextInt());
                record.setFirstName( input.next() );
                record.setLastName( input.next());
                record.setGrade( input.nextDouble());

                System.out.printf( "%-10d%-12s%-12s%10.2f\n",
                record.getIDnumber(), record.getFirstName(),
                record.getLastName(), record.getGrade() );
            }
        }
        catch ( NoSuchElementException elementException )
        {
            System.err.println( "File improperly formed. ");
            input.close();
            System.exit(1);

        }
         catch ( IllegalStateException stateException)
        {
            System.err.println(" Error reading from file.");
            System.exit(1);
        }
        }
        public void closeFile()
        {
            if (input!= null )
                input.close();
        }
     }

Here is the fifth class

     public class ReadStudentTextFileTest 
    {

        public static void main(String[] args) 
        {

            ReadStudentTextFile application = new ReadStudentTextFile();

            application.openfile();
            application.readStudentRecords();
            application.closeFile();



        }

    }

Answer 1

I second trying to put the whole path instead.

For relative paths, if you're doing compiling and running in command line/terminal, you need to have that studentrecords.txt in the same directory of your code files.

If you're using an IDE, you need to put your studentrecords.txt under the src/ folder. This is assuming you're not in maven project setup; otherwise it should be put under /src/main/java/resources/ .

Hope this helps!

Answer 2

Instead of creating a file every time you read from it, you should try using a FileReader wrapped in a BufferedReader.

Change this:

input = new Scanner( new File( "studentrecords.txt"));

To:

input = new Scanner(new BufferedReader(new FileReader("studentrecords.txt")));

See the tutorial for the Scanner class for more info.

Also make sure that the file you're trying to read from exists. That is, it should be on the same folder as your code. Another easy option is to try providing the full path to the file.