试图获得奖励积分，但我无法设置书籍的价值

Question

你好，我正在学习 java class 并且我将这个程序作为作业。我试图找出谁来设置值和 return 使用 Scanner class 的计算。我是 java（任何语言）的初学者。如果你能帮我弄清楚这个问题。我到处都找了，但找不到解决方案。

/**
* Write a description of class BookclubTester here.
*
* @author (your name)
* @version (a version number or a date)
*/
    import java.util.Scanner;  

    public class BookclubTester {

        public BookclubTester() {
            String  studentName;
        } 
 
        public static void main (String [] args) {
 
            int books;  
            int count = 0;
            while (count < 5) {
                Scanner input = new Scanner(System.in);

                System.out.println("Please provided your name :" );
                String studentName = input.nextLine();
    
                Bookclub rewardsProgram = new Bookclub();
                System.out.println("Please provide the numbers of books purchase for the  month " );
                books = input.nextInt();
     
                rewardsProgram.setBooks(books);
   
                System.out.println(rewardsProgram.getRewardPoints());
                count++;
            }
        }
   }

这是class

/**
*
* @author
*/
public class Bookclub {

    private  String studentName;
    private int books = 0;
    private  int rewardPoints;

    public Bookclub () {
 
    }

    public int getBooks() {
        return books;
    }

    public void setBooks(int books) {
        this.books = books;
    }

    public int getCalculateRewardPoints (){
        return rewardPoints;
    }

    public int getRewardPoints() {
        return rewardPoints;
    }

    public void setCalculateRewardPoints (int rewardPoints) {
        this.rewardPoints = rewardPoints;
        if (books == 0) {
            rewardPoints = 0;
            System.out.println("Your points are:" + rewardPoints);
       } else if (books == 1) {
            rewardPoints = 5;
       }else if (books == 2) {
            rewardPoints = 15;//
       }else if(books == 3) {
            rewardPoints = 30;
       }else if(books == 4) {
            rewardPoints = 60;
       } 
    }

    public void setRewardPoints(int rewardPoints) {
        this.rewardPoints = rewardPoints;
            if(rewardPoints == 0) {
                rewardPoints = 0;
            }else if(rewardPoints ==5) {
                System.out.println("Your points are : " + rewardPoints);
            }else if(rewardPoints == 15) {
                System.out.println("Your points are:" + rewardPoints);
            }else if(rewardPoints == 30) { 
                System.out.println("Your points are:" + rewardPoints);
            }else if(rewardPoints == 60) { 
                System.out.println("Your points are:" + rewardPoints);
            }  
        }
}

Answer 1

你的代码有点混乱，但对于初学者来说这是正常的:)

首先，在您的主要 class 中，您正在打印 rewardsProgram.getRewardPoints() 只是简单地 returns rewardPoints 为空！

当您在 setBooks 方法中设置书籍时，您必须调用第二个方法来计算您的 rewardsPoints，在您的例子中是 setRewardsPoints。在这个方法中，你必须使用你的变量 books 来获得你的分数，你可以使用类似的东西：

switch(books){
  case 0:
   rewardsPoints=0; break;
  case 1:
   rewardsPoints=5; break;
  ...
}

这就是您计算积分的方式。要打印 rewardsPoints，只需执行以下操作：

System.out.println(rewardsProgram.getRewardPoints());

你的class也需要理清一点，有些方法是没用的！这是完成所需操作的简单方法。

Answer 2

您应该解决代码中存在的以下问题：

构造函数里面的声明String studentName;，BookclubTester(){}没用
您既没有为 studentName 定义 setter 和 getter 方法，也没有将其设置到对象中，rewardsProgram。
在 while 循环之外实例化 Scanner 即 Scanner input = new Scanner(System.in); 应该在 while 循环之外。您可以重用在 while 循环外实例化的相同 Scanner 对象。
我还建议您使用 Integer.parseInt(input.nextLine()) 而不是 input.nextInt() 以避免 here.
您还没有将 rewardPoints 设置到对象 rewardsProgram 中。理想情况下，应该从 setBooks 调用 calculating/setting 奖励积分方法，因为奖励积分是基于书籍数量的。
书本数超过4时的奖励积分应该有一个条件（例如if (books >= 4)）。

下面给出了包含这些建议的代码：

import java.util.Scanner;

class Bookclub {

    private String studentName;
    private int books = 0;
    private int rewardPoints;

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public int getBooks() {
        return books;
    }

    public void setBooks(int books) {
        this.books = books;
        setRewardPoints(books);
    }

    public int getCalculateRewardPoints() {
        return rewardPoints;
    }

    public int getRewardPoints() {
        return rewardPoints;
    }

    public void setRewardPoints(int books) {
        if (books == 0) {
            rewardPoints = 0;
        } else if (books == 1) {
            rewardPoints = 5;
        } else if (books == 2) {
            rewardPoints = 15;//
        } else if (books == 3) {
            rewardPoints = 30;
        } else if (books >= 4) {
            rewardPoints = 60;
        }
    }
}

public class Main {

    public static void main(String[] args) {
        int books;
        int count = 0;
        Scanner input = new Scanner(System.in);

        while (count < 5) {
            Bookclub rewardsProgram = new Bookclub();

            System.out.print("Please provided your name: ");
            String studentName = input.nextLine();
            rewardsProgram.setStudentName(studentName);

            System.out.print("Please provide the numbers of books purchase for the  month: ");
            books = Integer.parseInt(input.nextLine());
            rewardsProgram.setBooks(books);

            System.out.println("Reward points: " + rewardsProgram.getRewardPoints());
            count++;
        }
    }
}

样本运行:

Please provided your name: Test1
Please provide the numbers of books purchase for the  month: 2
Reward points: 15
Please provided your name: Test2
Please provide the numbers of books purchase for the  month: 1
Reward points: 5
Please provided your name: Test3
Please provide the numbers of books purchase for the  month: 7
Reward points: 60
Please provided your name: Test4
Please provide the numbers of books purchase for the  month: 0
Reward points: 0
Please provided your name: Test5
Please provide the numbers of books purchase for the  month: 4
Reward points: 60

您仍然可以想到许多验证（例如检查书的数量是否不是负数），我希望这些建议能帮助您设计这些东西的程序。

Answer 3

public class BookClubMember {

    private final String name;
    private int books;
    private int rewardPoints;

    public BookClubMember(String name, int numberOfBooks) {
            this.name = name;
            setBooks(numberOfBooks);
    }

    public BookClubMember(String name) {
            this(name, 0);

    }

    public final String getName() {
            return name;
    }

    public final int getBooks() {
            return books;
    }

    public final void setBooks(int numberOfBooks) {
            int oldValue = books;
            if (numberOfBooks <= 0) {
                books = 0;
            } else {
                books = numberOfBooks;
            }
            if (oldValue != books) {
                // update your points if they have changed.
                rewardPoints = calculateRewardPoints(books);
            }
    }

        
    public final int getRewardPoints() {
            return rewardPoints;
    }

        /**
         * This can be overridden in the future if you ever wanted to extend
         * this class and make a "Platinum Member"... etc where they get more points
         * per book, or they are on a linear scale, etc etc.
         * 
         *
         * @param bookCount
         * @return
         */
        protected int calculateRewardPoints(int bookCount) {
            switch (bookCount) {
                case 0:
                    return 0;
                case 1:
                    return 5;
                case 2:
                    return 15;
                case 3:
                    return 30;
                default:
                    return 60;
            }
        }
    }

还有你的主要方法

 public static void main(String[] args) {
    
            // so you need to work in a scanner object here to collect a name, and number of books.
            // once you have both you can create a new BookClubMember object.
            // I'm cheating and manually putting them in :)
            BookClubMember member = new BookClubMember("Johnny", 5);
            System.out.println(member.getName() + " has " + member.getRewardPoints() + " points " + " for " + member.getBooks() + " books");
        }

输出：

Johnny has 60 points for 5 books

试图获得奖励积分，但我无法设置书籍的价值

trying to get the reward points and I can't set the value of Books

java

setvalue

这是class