java - DeleteByName 方法未从 randomAccessFile 中删除

Question

嘿，我的 RandomAccessFile 应用程序不适用于我的 deleteByName 方法。基本上我希望这个方法在商店中搜索学生，然后将其从 RandomAccessFile 中删除。搜索位没有问题，但 RandomAccessFile 仍然显示该员工的详细信息为空，而不是完全删除该学生。有人可以帮忙吗？

这是我的代码:

//---------------------------------------------------------------------------------------
//          Name:        Case 3: Delete by Name.
//          Description: Choice 3 gives the user an option to delete an employee by name.
//---------------------------------------------------------------------------------------
                    case 3:
                        System.out.println("Delete by Name.");
                        Student studentDelete = MenuMethods.userInputByName();
                        details.searchByName(studentDelete.getStudentName());
                        details.remove(studentDelete.getStudentName());
                        file.write(studentDelete.toString().getBytes());
                        break;

学生商店

// ---------------------------------------------------------------------------------------
    // Name: Search by Name.
    // ---------------------------------------------------------------------------------------
    public Student searchByName(String studentName)
    {
        Student student = map.get(studentName);
        System.out.println(student);
        return student;
    }
 public void write(RandomAccessFile file) throws IOException
        {
            for (Student student : map.values())
            {
                byte[] bytes = student.toString().getBytes();
                for(byte byteWrite : bytes)
                {
                    file.writeByte(byteWrite);
                }
            }

        }

        public void readAll(RandomAccessFile file) throws IOException
        {
            /*final int Record_Length = 30;
            int recordNumber = 0;
            file.seek((recordNumber) * Record_Length);

            String code ="";
            for(int i = 0; i < 30; i++)
            {
            code += file.readLine() + "\n";
            }
            System.out.println(code);*/
            file.seek(0);

            String code;
            while((code = file.readLine())!=null)
            System.out.println(code);

        }

    // ---------------------------------------------------------------------------------------
    // Name: Remove.
    // ---------------------------------------------------------------------------------------
    public Student remove(String key) 
    {
        // Remove the Employee by name.
        if (map.containsKey(key))
            return map.remove(key); // if it is there remove and return
        else
            return null; // if its not there return nothing.
    }

菜单方法

//---------------------------------------------------------------------------------------
//  Name:           Imports. 
//  Description:    To allow the use of different Java classes.
//---------------------------------------------------------------------------------------
import java.util.Scanner;
//---------------------------------------------------------------------------------------

public class MenuMethods 
{
    private static Scanner keyboard = new Scanner(System.in);
//---------------------------------------------------------------------------------------
//  Methods for the Company Application menu.
//---------------------------------------------------------------------------------------

//---------------------------------------------------------------------------------------
//  Name:           getMenuChoice.
//  Description:    Method for validating the choice.
//---------------------------------------------------------------------------------------
    public static int getMenuChoice(String menuString, int limit,String prompt, String errorMessage) 
    {
        System.out.println(menuString);
        int choice = inputAndValidateInt(1, limit, prompt, errorMessage);
        return choice;
    }

//---------------------------------------------------------------------------------------
//  Name:        inputAndValidateInt.
//  Description: This method is used in the getMenuChoice method.
//---------------------------------------------------------------------------------------
    public static int inputAndValidateInt(int min, int max, String prompt,String errorMessage) 
    {
        int number;
        boolean valid;
        do 
        {
            System.out.print(prompt);
            number = keyboard.nextInt();
            valid = number <= max && number >= min;
            if (!valid) 
            {
                System.out.println(errorMessage);
            }
        } while (!valid);
        return number;
    }

//---------------------------------------------------------------------------------------
//  Name:        userInput
//  Description: This method is used in the MainApp to give the user capability to enter
//               the details when adding details of an employee into the store.
//---------------------------------------------------------------------------------------
    public static Student userInput() 
    {
        String temp = keyboard.nextLine();
        Student s = null;
        System.out.println("Please enter the Student Name:");
        String studentName = keyboard.nextLine();
        System.out.println("Please enter the Student ID:");
        String studentId = keyboard.nextLine();
        System.out.println("Please enter the Student E-mail address:");
        String studentEmail = keyboard.nextLine();
        System.out.println("Please enter the Student telephone number:");
        String studentTelephoneNumber = keyboard.nextLine();
        return s = new Student(studentName, studentId, studentEmail,studentTelephoneNumber);

    }

//---------------------------------------------------------------------------------------
//  Name:        userInputByName.
//  Description: This method is used in the MainApp to give the user capability to search by name.
//---------------------------------------------------------------------------------------
    public static Student userInputByName() 
    {
        // String temp is for some reason needed. If it is not included
        // The code will not execute properly.
        String temp = keyboard.nextLine();
        Student s = null;
        System.out.println("Please enter the Student Name:");
        String studentName = keyboard.nextLine();

        return s = new Student(studentName);

    }

//---------------------------------------------------------------------------------------
//  Name:        userInputByEmail
//  Description: This method is used in the MainApp to give the user capability to search by email.
//---------------------------------------------------------------------------------------
    public static String userInputByEmail() 
    {
        // String temp is for some reason needed. If it is not included
        // The code will not execute properly.
        String temp = keyboard.nextLine();
        Student s = null;
        System.out.println("Please enter the StudentEmail:");
        String studentEmail = keyboard.nextLine();
        // This can use the employeeName's constructor because java accepts the
        // parameters instead
        // of the name's.
        return studentEmail;

    }
//---------------------------------------------------------------------------------------
}

商店是使用 HashMap 组成的。

Answer 1

您似乎在删除时再次写入学生条目。

file.write(studentDelete.toString().getBytes());

也许您需要将这些字节清零，或将其留空或执行一些特殊操作，这意味着该条目已被删除。