How do I fix "error: constructor (class) in class (class) cannot be applied to given types;"

Question

所以我正在编写这段代码来创建一个使用抽象类或诸如此类的东西的小型数据库类型程序。我已经找到我的驱动程序代码，我正在其中创建 2 个新对象；一个带有随机参数，另一个带有第一个对象。

Student test1 = new Student("Jack", "jackjack@test.com", "Math", 3.9, 10);
BandMember test2 = new BandMember(test1);

但是当我运行我的程序时，出现这个错误：

CollegeDatabase.java:122: error: constructor BandMember in class BandMember cannot be applied to given types;
    BandMember test2 = new BandMember(test1);
                       ^
required: String,String,String,double,int
found: Student
  reason: actual and formal argument lists differ in length
1 error

我真的很困惑为什么会出现这个错误。如果有人能帮我解决这个问题，我将不胜感激。谢谢！

（请记住，我目前是 java 的新手：我）

这是我的 CollegeDatabase.java:

abstract class Person{
    public String emailAddress, personName;
    
    public Person(String name, String email){
        System.out.println("created person");
        name = personName;
        email = emailAddress;
    }
    
    public String returnName(){
        return personName;
    }
    
    public String returnEmail(){
        return emailAddress;
    }
    
    public void editName(String newName){
        personName = newName;
        System.out.println("successfully changed name");
    }
    
    public void editEmail(String newEmail){
        emailAddress = newEmail;
        System.out.println("successfully changed email");
    }
}

class Student extends Person{
    public String majorSubject;
    public double gradePointAverage;
    public int gradeLevel;
    
    public Student(String name, String email, String major, double gpa, int grade){
        super(name, email);
        major = majorSubject;
        gpa = gradePointAverage;
        grade = gradeLevel;
    }
    
    public void changeGPA(double newGPA){
        gradePointAverage = newGPA;
        System.out.println("changed gpa");
    }
    
    public void changeMajor(String newMajor){
        majorSubject = newMajor;
        System.out.println("changed major");
    }
    
    public void changeGrade(int newGrade){
        gradeLevel = newGrade;
        System.out.println("changed grade");
    } 
    
    
    public double getGPA(){
        return gradePointAverage;
    }
    
    public String getMajor(){
        return majorSubject;
    }
    
    public int getGrade(){
        return gradeLevel;
    }
    public String toString(){
        return "Name: "+personName+", Email: "+emailAddress+", Major: "+majorSubject+", GPA: "+gradePointAverage+", Grade: "+gradeLevel+"th";
    }
}

class BandMember{
    private String name, email, major, instrument;
    private double gpa;
    private int grade;
    
    public BandMember(String name, String email, String major, double gpa, int grade){
        this.name = name;
        this.email = email;
        this.major = major;
        this.gpa = gpa;
        this.grade = grade;
        System.out.println("created new band member");
    }
    public void assignInstruments(){
        if(grade == 9){
            instrument = "bells";
        }
        else if(grade == 10){
            instrument = "trumpet";
        }
        else if(grade == 11){
            instrument = "baritone";
        }
        else if (grade == 12){
            instrument = "tuba";
        }
    }
    public void changeInstrument(String instrument){
        this.instrument = instrument;
        System.out.println("successfuly changed instruments");
    }
    
    public String toString(){
        return "Name: "+name+", Email: "+email+", Major: "+major+", GPA: "+gpa+", Grade: "+grade+"th, Instrument: "+instrument;
    }
}

public class CollegeDatabase{
    
    public static void main(String[] args)
    {
        Student test1 = new Student("Jack", "jackjack@test.com", "Math", 3.9, 10);
        
        test1.editName("Jill");
        test1.editEmail("jilljill@test.com");
        test1.changeGPA(4.0);
        test1.changeMajor("computer science");
        test1.changeGrade(11);
        
        BandMember test2 = new BandMember(test1);
        //error is above ^
        test2.assignInstruments();

        System.out.println(test1);
        System.out.println(test2);
    }
}

Answer 1

Bandmember class 中没有接受学生作为参数的构造函数。构造函数当前看起来像这样：public BandMember(String name, String email, String major, double gpa, int grade)。我了解到您可能想要创建一个带有 student 的新 Bandmember。然后你可以在 Bandmember class 中创建另一个构造函数。这是一个应该可以使用的模板。

public BandMember(Student student){
    this.name = student.returnName();
    this.email = student.returnEmail();
    this.major = student.getMajor();
    this.gpa = student.getGPA();
    this.grade = student.getGrade();
    System.out.println("created new band member");
}

How do I fix "error: constructor (class) in class (class) cannot be applied to given types;"

How do I fix "error: constructor (class) in class (class) cannot be applied to given types;"

java

class

object