Java Eclipse-未定义的构造函数和方法

Question

错误在底部的主类中，我在代码中详细列出了它们以及它们的错误消息。 我的Session构造函数中也有一个super（）关键字，可以从Customer类中调用方法。 我只想运行我的程序，但是每次我修复一个问题时，另一个（或两个）问题就会取代它。 请帮忙！

import java.util.*;

public class Main 
{
public class Customer 
{
   public String Name = "";
   public int ID = 0000;
   public int plansLeft = 0;


   public Customer()
    {
    }

   public Customer (String n, int id, int pl) 
   {
      Name = n;
      ID = id;
      plansLeft = pl;
   }
   public void setName(String n)
   {
      Name = n;  
   }
   public void setidnumber(int id)
   {
       ID = id;
   } 
   public void setPlansLeft(int pl)
   {
       plansLeft = pl;
   }


   public String getName()
   {
      return Name;
   }
   public int getIDNumber()
   {
      return ID;
   }
   public int getPlansLeft()
   {
      return plansLeft;
   }
}


public class Session extends Customer 
{   
    public int sessionIDNumber = 0000;
    public int spotsLeft = 0;

    public Session()
    {
    }

    public Session (String Name, int ID, int plansLeft, int sID, int sl) 
       {
        super(Name, ID, plansLeft); // <----- perhaps an issue here?
        sessionIDNumber = sID;
        spotsLeft = sl;
       }


    public int getsessionIDNumber() {
        return sessionIDNumber;
    }

    public int getspotsLeft() {
        return spotsLeft;
    }

    public void setsessionIDNumber(int sessionIDNumber) {
        this.sessionIDNumber = sessionIDNumber;
    }

    public void setspotsLeft(int sl) {
        this.spotsLeft = sl;
    }
}




public static void main(String[] args) 
{
    //public Customer(){}    // <----- tried using this but only adds more errors

    Customer customer = new Customer("Sarah", 12345678, 12, 0117, 0); // < ----- error is here: "The constructor Main.Customer(String, int, int, int, int) is undefined"

    System.out.println("Customer Name: " + customer.getName() + "\nCustomer ID: " + customer.getIDNumber() + "\nLessons Remaining: " + customer.getPlansLeft());
    System.out.println("\nSession ID: " + customer.getsessionIDNumber() + "\nOpen Spots Available: " + customer.getspotsLeft()); // < ------ couple more errors here: "The method getsessionIDNumber/getspotsLeft() is undefined for the type Main.Customer"
}
}

Answer 1

将客户类定义为静态。 这是示例：

  public class Main 
{
public static class Customer 
{
   public String Name = "";
   public int ID = 0000;
   public int plansLeft = 0;


   public Customer()
    {
    }

   public Customer (String n, int id, int pl) 
   {
      Name = n;
      ID = id;
      plansLeft = pl;
   }
   public void setName(String n)
   {
      Name = n;  
   }
   public void setidnumber(int id)
   {
       ID = id;
   } 
   public void setPlansLeft(int pl)
   {
       plansLeft = pl;
   }


   public String getName()
   {
      return Name;
   }
   public int getIDNumber()
   {
      return ID;
   }
   public int getPlansLeft()
   {
      return plansLeft;
   }
}


public class Session extends Customer 
{   
    public int sessionIDNumber = 0000;
    public int spotsLeft = 0;

    public Session()
    {
    }

    public Session (String Name, int ID, int plansLeft, int sID, int sl) 
       {
        super(Name, ID, plansLeft); // <----- perhaps an issue here?
        sessionIDNumber = sID;
        spotsLeft = sl;
       }


    public int getsessionIDNumber() {
        return sessionIDNumber;
    }

    public int getspotsLeft() {
        return spotsLeft;
    }

    public void setsessionIDNumber(int sessionIDNumber) {
        this.sessionIDNumber = sessionIDNumber;
    }

    public void setspotsLeft(int sl) {
        this.spotsLeft = sl;
    }
}




public static void main(String[] args) 
{
    //public Customer(){}    // <----- tried using this but only adds more errors

    Customer customer = new Customer("Sarah", 12345678, 12); // < ----- error is here: "The constructor Main.Customer(String, int, int, int, int) is undefined"

    System.out.println("Customer Name: " + customer.getName() + "\nCustomer ID: " + customer.getIDNumber() + "\nLessons Remaining: " + customer.getPlansLeft());
//    System.out.println("\nSession ID: " + customer.getsessionIDNumber() + "\nOpen Spots Available: " + customer.getspotsLeft()); // < ------ couple more errors here: "The method getsessionIDNumber/getspotsLeft() is undefined for the type Main.Customer"
}
}

Answer 2

记住一件事，当您使用继承时，总是创建child（sub）类的对象。 在您的情况下，Session是其中有五个参数但创建了没有五个参数的Customer类的子类。

Customer customer = new Customer("Sarah", 12345678, 12, 0117, 0);

此行发出错误，因为Customer类没有五个参数。

Customer和Session类都存在于Main类中，因此它们的对象可通过Main类对象进行访问。

使用下面的代码而不是上面的代码-

Session session= new Main().new  Session("Sarah", 12345678, 12, 0117, 0);

创建子类对象时，它也会调用父类构造函数。 对于您的评论，请使用会话对象调用所有内容，

System.out.println("Customer Name: " + session.getName() + "\nCustomer ID: " + session.getIDNumber() + "\nLessons Remaining: " + session.getPlansLeft());
    System.out.println("\nSession ID: " + session.getsessionIDNumber() + "\nOpen Spots Available: " + session.getspotsLeft());

Answer 3

尝试这个：
Customer customer = new Main().new Customer("Sarah", 12345678, 12)