Question

我的DeleteByName方法出错了。错误是：

StudentStore类型中的delete（Student）方法不适用于参数（String）

我知道这与方法本身的参数错误有关，但我不知道如何修复它。之后我无法让学生真正从文本文件中删除。商店使用Arraylist制作。有五个学生被宣布，我有添加方法工作。

这是我的代码：

MainApp

//---------------------------------------------------------------------------------------
//          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.deleteByName(studentDelete.getStudentName());
                        break;

StudentStore

// ---------------------------------------------------------------------------------------
// Name: DeleteByName.
// ---------------------------------------------------------------------------------------
    public boolean deleteByName(Student s) 
    {
        if(students.remove(s))
            return students.remove(s);
            else
            return false;
}

public Student searchByName(String employeeName)
    {
        Student employee = Student.get(employeeName);
        System.out.println(employee);
        return employee;
    }

// ---------------------------------------------------------------------------------------
// Name: Search by Email.
// ---------------------------------------------------------------------------------------
public String searchByEmail(String studentEmail) 
{
    for (Student student : map.values()) 
    {
        if (student.getStudentEmail().equals(studentEmail) 
        {
            System.out.println(student.getStudentEmail());
            return student.getStudentEmail();
        }
    }
    return null;
}

MenuMethods

//---------------------------------------------------------------------------------------
//  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;

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

Answer 1

使用错误的参数（String）

调用deleteByName方法

details.deleteByName(studentDelete.getStudentName());

但它希望学生

public boolean deleteByName(Student s)

您应将其更改为：

public boolean deleteByName(String name){

你的第二个问题是删除过程本身。您必须删除一个对象：

public boolean deleteByName(String name){
    Student s = new Student(name);
    return students.remove(s);
}

要从列表中删除Object，您需要在Student类中使用equals-Method。如果没有该方法，删除无法找到要删除的正确对象（用您的学生类中的正确属性名称替换名称！）：

public boolean equals(Object b){
    if(this.name.equals(b.name)){
        return true;
    }
    return false;
}

Answer 2

details.deleteByName(studentDelete.getStudentName());

在您的上一行中传递String类型。

更改您的删除方法

public boolean deleteByName(String s) 
    {
        if(students.remove(s))
            return students.remove(s);
            else
            return false;
}

Answer 3

你没有提到你到底发生了什么错误。

您的代码存在许多问题：

deleteByName方法的签名是deleteByName(Student s)，但您可以这样调用它：deleteByName(studentDelete.getStudentName())，其实际参数似乎是一个String。问题在于deleteByName方法的声明。鉴于其名称，您应该将其声明为期望名称作为参数（最可能是String）：
```
public boolean deleteByName(String name);
```

您删除相同的名称2次：

if(students.remove(s))
    return students.remove(s);
    else
    return false;

试试这个：

return students.remove(s) != null;

Answer 4

// ---------------------------------------------------------------------------------------
// Name: Remove.
// ---------------------------------------------------------------------------------------
     public void delete(String s)
     {
         students.remove(s);
     }

然后在MainApp

中

case 3:
                        System.out.println("Delete by Name.");
                        Student studentDelete = MenuMethods.userInputByName();
                        details.searchByName(studentDelete.getStudentName());
                        details.delete(studentDelete.getStudentName());
                        break;

DeleteByName方法不适用于RandomAccessFile

4 个答案: