Java 我怎样才能保持我的变量是私有的，并且仍然获得所需的输出？_Java_Private

Java 我怎样才能保持我的变量是私有的，并且仍然获得所需的输出？

java

Java 我怎样才能保持我的变量是私有的，并且仍然获得所需的输出？,java,private,Java,Private,我的作业要求我们将以下变量设置为私有，如图所示：私有字符串标题；私人双价--------这些变量可以在Book.java文件中找到我的代码无法检索这些变量，因为它们在textube.java文件中不可见。如何使这些变量保持私有，但在运行TextbookApp.java文件时仍能获得所需的输出。以下是所需的输出：下面是我现在得到的输出： Book.java package assignment2; public class Book { private String title; p

我的作业要求我们将以下变量设置为私有，如图所示：私有字符串标题；私人双价--------这些变量可以在Book.java文件中找到

我的代码无法检索这些变量，因为它们在textube.java文件中不可见。如何使这些变量保持私有，但在运行TextbookApp.java文件时仍能获得所需的输出。以下是所需的输出：

下面是我现在得到的输出：

Book.java

package assignment2;

public class Book {

private String title;
private double price; 

    public Book ()
    {
        title = "";
        price = 0.0;
    }
    
    public Book (String t, double p)
    {
        title = t;
        price = p;  
    }   
    public void setTitle(String t)
    {
        title = t; 
    }
    
    public String getTitle()
    {
        return title;
    }
    
    public void setPrice(double p)
    {
        price = p;
    }
    
    public double getPrice()
    {
        return price;
    }
    
    public String toString()
    {
        return title + " " + price; 
    }
}

package assignment2;

public class BookApp {

    public static void main(String[] args) {
        Book b1 = new Book();
        b1.setTitle("John Doe");
        b1.setPrice(8.5);
        System.out.println(b1.toString());

        Book b2 = new Book("Ann Smith", 9.7);
        System.out.println(b2.toString());
    }

}

package assignment2;

public class Textbook extends Book{
    private int courseID;
    
    public Textbook()
    {
        title = "";
        price = 0.0;
        courseID = 0;
    }
    
    public Textbook (String t, double p, int ID)
    {
        title = t;
        price = p;
        courseID = ID;
    }
    
    public void setCourseID(int ID)
    {
        courseID = ID;
    }
    
    public int getCourseID()
    {
        return courseID;
    }
    
    public String toString()
    {
        return title + " " + price + " " + courseID; 
    }
}

package assignment2;

public class TextBookApp extends Textbook {

    public static void main(String[] args) {
        Book b = new Book ("Ann Smith", 9.7);
        System.out.println(b.toString());
        
        Textbook tb1 = new Textbook();
        tb1.setTitle("John Doe");
        tb1.setPrice(8.5);
        tb1.setCourseID(2050);
        System.out.println(tb1.toString());
        
        Textbook tb2 = new Textbook("Ann Smith", 9.7, 3090);
        System.out.println(tb2.toString());
    }

}

BookApp.java

package assignment2;

public class Book {

private String title;
private double price; 

    public Book ()
    {
        title = "";
        price = 0.0;
    }
    
    public Book (String t, double p)
    {
        title = t;
        price = p;  
    }   
    public void setTitle(String t)
    {
        title = t; 
    }
    
    public String getTitle()
    {
        return title;
    }
    
    public void setPrice(double p)
    {
        price = p;
    }
    
    public double getPrice()
    {
        return price;
    }
    
    public String toString()
    {
        return title + " " + price; 
    }
}

package assignment2;

public class BookApp {

    public static void main(String[] args) {
        Book b1 = new Book();
        b1.setTitle("John Doe");
        b1.setPrice(8.5);
        System.out.println(b1.toString());

        Book b2 = new Book("Ann Smith", 9.7);
        System.out.println(b2.toString());
    }

}

package assignment2;

public class Textbook extends Book{
    private int courseID;
    
    public Textbook()
    {
        title = "";
        price = 0.0;
        courseID = 0;
    }
    
    public Textbook (String t, double p, int ID)
    {
        title = t;
        price = p;
        courseID = ID;
    }
    
    public void setCourseID(int ID)
    {
        courseID = ID;
    }
    
    public int getCourseID()
    {
        return courseID;
    }
    
    public String toString()
    {
        return title + " " + price + " " + courseID; 
    }
}

package assignment2;

public class TextBookApp extends Textbook {

    public static void main(String[] args) {
        Book b = new Book ("Ann Smith", 9.7);
        System.out.println(b.toString());
        
        Textbook tb1 = new Textbook();
        tb1.setTitle("John Doe");
        tb1.setPrice(8.5);
        tb1.setCourseID(2050);
        System.out.println(tb1.toString());
        
        Textbook tb2 = new Textbook("Ann Smith", 9.7, 3090);
        System.out.println(tb2.toString());
    }

}

教科书.java

package assignment2;

public class Book {

private String title;
private double price; 

    public Book ()
    {
        title = "";
        price = 0.0;
    }
    
    public Book (String t, double p)
    {
        title = t;
        price = p;  
    }   
    public void setTitle(String t)
    {
        title = t; 
    }
    
    public String getTitle()
    {
        return title;
    }
    
    public void setPrice(double p)
    {
        price = p;
    }
    
    public double getPrice()
    {
        return price;
    }
    
    public String toString()
    {
        return title + " " + price; 
    }
}

package assignment2;

public class BookApp {

    public static void main(String[] args) {
        Book b1 = new Book();
        b1.setTitle("John Doe");
        b1.setPrice(8.5);
        System.out.println(b1.toString());

        Book b2 = new Book("Ann Smith", 9.7);
        System.out.println(b2.toString());
    }

}

package assignment2;

public class Textbook extends Book{
    private int courseID;
    
    public Textbook()
    {
        title = "";
        price = 0.0;
        courseID = 0;
    }
    
    public Textbook (String t, double p, int ID)
    {
        title = t;
        price = p;
        courseID = ID;
    }
    
    public void setCourseID(int ID)
    {
        courseID = ID;
    }
    
    public int getCourseID()
    {
        return courseID;
    }
    
    public String toString()
    {
        return title + " " + price + " " + courseID; 
    }
}

package assignment2;

public class TextBookApp extends Textbook {

    public static void main(String[] args) {
        Book b = new Book ("Ann Smith", 9.7);
        System.out.println(b.toString());
        
        Textbook tb1 = new Textbook();
        tb1.setTitle("John Doe");
        tb1.setPrice(8.5);
        tb1.setCourseID(2050);
        System.out.println(tb1.toString());
        
        Textbook tb2 = new Textbook("Ann Smith", 9.7, 3090);
        System.out.println(tb2.toString());
    }

}

TextbookApp.java

package assignment2;

public class Book {

private String title;
private double price; 

    public Book ()
    {
        title = "";
        price = 0.0;
    }
    
    public Book (String t, double p)
    {
        title = t;
        price = p;  
    }   
    public void setTitle(String t)
    {
        title = t; 
    }
    
    public String getTitle()
    {
        return title;
    }
    
    public void setPrice(double p)
    {
        price = p;
    }
    
    public double getPrice()
    {
        return price;
    }
    
    public String toString()
    {
        return title + " " + price; 
    }
}

package assignment2;

public class BookApp {

    public static void main(String[] args) {
        Book b1 = new Book();
        b1.setTitle("John Doe");
        b1.setPrice(8.5);
        System.out.println(b1.toString());

        Book b2 = new Book("Ann Smith", 9.7);
        System.out.println(b2.toString());
    }

}

package assignment2;

public class Textbook extends Book{
    private int courseID;
    
    public Textbook()
    {
        title = "";
        price = 0.0;
        courseID = 0;
    }
    
    public Textbook (String t, double p, int ID)
    {
        title = t;
        price = p;
        courseID = ID;
    }
    
    public void setCourseID(int ID)
    {
        courseID = ID;
    }
    
    public int getCourseID()
    {
        return courseID;
    }
    
    public String toString()
    {
        return title + " " + price + " " + courseID; 
    }
}

package assignment2;

public class TextBookApp extends Textbook {

    public static void main(String[] args) {
        Book b = new Book ("Ann Smith", 9.7);
        System.out.println(b.toString());
        
        Textbook tb1 = new Textbook();
        tb1.setTitle("John Doe");
        tb1.setPrice(8.5);
        tb1.setCourseID(2050);
        System.out.println(tb1.toString());
        
        Textbook tb2 = new Textbook("Ann Smith", 9.7, 3090);
        System.out.println(tb2.toString());
    }

}

您可以通过从

教科书

子类调用

书籍

中相应的超类构造函数或方法来解决此错误：

package assignment2;

public class Textbook extends Book{
    private int courseID;
    
    public Textbook()
    {
        courseID = 0;
    }
    
    public Textbook (String t, double p, int ID)
    {
        super(t, p);
        courseID = ID;
    }
    
    public void setCourseID(int ID)
    {
        courseID = ID;
    }
    
    public int getCourseID()
    {
        return courseID;
    }
    
    public String toString()
    {
        return super.toString() + " " + courseID; 
    }
}

无参数构造函数

Book（）

将自动调用无参数构造函数

Book（）

，因此您无需在

Book（）

中明确设置

标题和price
，请将错误消息作为文本而不是屏幕截图发布在此处。还要指出代码中导致错误的部分。