在主要活动中实现代码[暂停]

Question

我在使用用户输入创建对象以尝试完成以下分配时遇到问题：

一本书的title和price作为数据成员（私有数据成员）和一个 DISCOUNT 常量。 它有两个重载的构造函数，私有数据成员的getter和setter， toString方法和priceAfterDiscount方法，计算并返回折扣后的价格

我已经完成了 POJO Java class 但我需要帮助来实现代码，该代码采用用户输入在主 function 中创建 POJO 实例。

Book.java

public class Book {
    private String title;
    private double price;

    public static final double DISCOUNT=0.20;

    public Book(){
        title="Unkown";
        price=0.0;
    }

    public Book(String name, double cost){
        title=name;
        price=cost;
    }

    public void setTitle(String n){
        title=n;
    }

    public String getTitle(){
        return title;
    }

    public void setPrice(double p){
        price=p;
    }

    public double getPrice(){
        return price;
    }

    public double priceAfterDiscount() {
        if (price <= 0) {
            return 0;
        }
        return price - (price * DISCOUNT);
    }

    public String toString() {
        return title + " " + priceAfterDiscount();
    }
}

书店.java

import java.util.Scanner;

public class BookStore {
    static Scanner console= new Scanner(System.in);

    public static void main(String[]args){
        Book b1,b2;
        String title;
        double price,newPrice;

        System.out.print("Enter title: ");
        title=console.next();

        System.out.print("Enter price: ");
        price=console.nextDouble();

        /*
            Create a book object based on the user input for b1
            Call method priceAfterDiscount to get b1's new price 
            Print b1's information including title, price and newPrice
        */

        System.out.print("Enter another title: ");
        title=console.next();

        System.out.print("Enter another price: ");
        price=console.nextDouble();

        /*
            Create a book object based on the user input b2
        */

        /*
            Compare the original prices of b1 and b2 have the same original price
        */
        if() {    
            System.out.println("Same price");
        } else {
            System.out.println("Not Same Price");
        }
    }
}

Answer 1

在main中，先把main开头的书拿出来，因为我们会在inputs之后创建，在第一个inputs之后创建objects：

Book b1 = new Book(title, price);

在第二次输入之后

Book b2 = new Book(title, price);

而不是检查两者的价格是否相同：

if(b1.getPrice() == b2.getPrice()) System.out.println("Same price");
else System.out.println("Not Same Price");

Answer 2

您可以通过使用读取的值调用构造函数来简单地创建书 object，例如：

Book book = new Book(title, bookPrice);

在实例化两个 Book 对象后，您只需使用==运算符比较它们即可。

b1.getPrice() == b2.getPrice()

完全调整后的main() function 可能看起来像这样：

public static void main(String[]args){
    /* no need to set up variables early */

    System.out.print("Enter title: ");
    String firstBookTitle = console.next();

    System.out.print("Enter price: ");
    double firstBookPrice = console.nextDouble();

    // Create a book object based on the user input for b1
    Book b1 = new Book(firstBookTitle, firstBookPrice);

    // Call method priceAfterDiscount to get b1's new price
    double discountedPrice = b1.priceAfterDiscount();

    // Print b1's information including title, price and newPrice
    System.out.println("The book '" + b1.getTitle() + "' costs only " + discountedPrice + " instead of " + b1.getPrice());

    System.out.print("Enter another title: ");
    String secondBookTitle = console.next();

    System.out.print("Enter another price: ");
    double secondBookPrice = console.nextDouble();

    // Create a book object based on the user input b2
    Book b2 = new Book(secondBookTitle, secondBookPrice);

     // Compare the original prices of b1 and b2 have the same original price
    if(b1.getPrice() == b2.getPrice()) {
        System.out.println("Same price");
    } else {
        System.out.println("Not Same Price");
    }
}