如何添加priceAfterDiscount的公共方法，该方法返回折扣后的价格

Question

如何添加公共方法priceAfterDiscount，该方法在此类中返回折扣后的价格：

public class Book1 {
    private String title;
    private double price;

    public static final double DISCOUNT=0.20;

    public Book1(){
        title="Unkown";
        price=0.0;
    }

    public Book1(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();

}

这是我的主要活动。帮我写代码。

    import java.util.Scanner;
    public class BookStore {
    static Scanner console= new Scanner(System.in);
    public static void main(String[]args){
    Book1 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*/


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

b1原价加10美元（硬代码）

}

}

Answer 1

这应该有效：

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

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