努力使用多个类

Question

所以目前，我正在努力在 eclipse 中制作一个特定的程序来完成一项任务，虽然我能够制作大部分程序，但我似乎在为程序的无参数部分以及带来碎片而苦苦挣扎第一堂课暂时进入第二堂课。这是我的头等舱代码

// Preparation of the input
import java.util.Scanner;

public class primarySetUp {

public static void main(String[] args) {
    // Variable Declaration
    double userBagNumber;
    double userBagWeight;
    
    // Create Scanner
    Scanner input = new Scanner(System.in);
    java.util.Date date = new java.util.Date();
    
    // Opening Statement
    System.out.println("Welcome to the Coffee Sales Simulation!");
    
    // Get User Input
    System.out.println("How heavy do you want the bags to be?");
    userBagWeight = input.nextDouble();
    System.out.println("How many bags do you want?");
    userBagNumber = input.nextDouble();
    
    // Get output
    // Date
    System.out.println("Todays date:  ");
    System.out.printf("%tB %<te, %<tY", date);
    System.out.println(""); // spacer
    // Original Inputs
    System.out.printf("\nNumber of Bags: %3.0f", userBagNumber);
    System.out.printf("\nWeight of Each Bag: %3.2f", userBagWeight);
    System.out.print(" lbs");
    
    // Calling of the Class
    secondarySetUp mysecondarySetUp = new secondarySetUp(userBagWeight, userBagNumber);
    
    // End Program
    System.out.println("\nThank you for shopping with us!");
}

}

这是我的第二类代码，在这种情况下它充满了错误。

public class secondarySetUp {
    
    // Constants
    static double pricePerPound = 5.99;
    static double taxRate = 0.0725;
    
    int singleBagger, pounderBagger;
    public secondarySetUp(double userBagWeight, double userBagNumber) {
    
        
        
        
    //  A method named getTaxRate() that returns the tax rate.  
        
        System.out.printf("\nPrice per Pound: $%2.2f", getPrice());
        System.out.printf("\nSales Tax: $%2.2f", getTaxRate());
        System.out.print(" %");
        System.out.printf("\nPrice of one bag weighing one pound: %3.2f", getSale());
        
    }
    // No argument pricing
    public Sale() {
            singleBagger = 1;
            pounderBagger = 1;
        }
    // First constructor receiving No argument pricing
    public Sale(int w, int n) {
            singleBagger = w;
            pounderBagger = n;
        }
    // Sale without tax
    public double getSale() {
        return userBagWeight * singleBagger * pounderBagger;
    }
    // Get Sale Tax
    public double getSaleTax() {
        return (getSale() * taxRate);
    }
    // Get total pricing
    public double getTotalPrice() {
        return (getSale() + getSaleTax());
    }
    public double getPrice() {
        return pricePerPound;
    }
    public double getTaxRate() {
        return taxRate * 100;
    }
}

如果您有任何我可以应用的修复方法，请告诉我；我还计划为其余参数添加打印语句，但我想先修复 Sale()。

Answer 1

我在getSale() 中看到一个问题，您尝试使用userBagWeight，但该变量在构造函数参数之外不存在，这可能会产生很多问题，因为其他methods 正在调用它。构造函数采取 double userBagWeight, double userBagNumber，但它没有将它们分配给任何字段或对它们做任何事情。

我错过了您将Sale() 视为constructor 的部分，但那些不是constructors。 constructor 以你的类名命名。

public secondarySetUp(double userBagWeight, double userBagNumber)

将Sale() 更改为secondarySetUp，你会没事的。

你的班级应该是这样的：

public class secondarySetUp {

// Constants
static double pricePerPound = 5.99;
static double taxRate = 0.0725;

int singleBagger, pounderBagger;
double userBagWeight, userBagNumber;
public secondarySetUp(double userBagWeight, double userBagNumber) {
    this.userBagWeight = userBagWeight;
    this.userBagNumber = userBagNumber;

    singleBagger = 1;
    pounderBagger = 1;
    
    
    
//  A method named getTaxRate() that returns the tax rate.  
    
    System.out.printf("\nPrice per Pound: $%2.2f", getPrice());
    System.out.printf("\nSales Tax: $%2.2f", getTaxRate());
    System.out.print(" %");
    System.out.printf("\nPrice of one bag weighing one pound: %3.2f", getSale());
    
}
// First constructor receiving No argument pricing
public secondarySetUp(int w, int n) {
        singleBagger = w;
        pounderBagger = n;
    }
// Sale without tax
public double getSale() {
    return userBagWeight * singleBagger * pounderBagger;
}
// Get Sale Tax
public double getSaleTax() {
    return (getSale() * taxRate);
}
// Get total pricing
public double getTotalPrice() {
    return (getSale() + getSaleTax());
}
public double getPrice() {
    return pricePerPound;
}
public double getTaxRate() {
    return taxRate * 100;
}

}

this 是一个关键字，告诉程序我们要使用字段“实例变量”，如果我们有一个带有 parameter 的方法与字段名称相同，那么为了区分它们，我们告诉程序this.fieldName 知道我们在说哪一个。