实例变量（来自另一个类的对象）

Question

我有一个主类Test和另外两个表示某些特定对象的类（Book，class Order）。从我的课Test我创建了5个Book对象。现在我想创建两个使用Order类中的方法的Order对象。具体使用setCustomerName（），SetCustomerAddress（），toString（）getTotlaPrice（）和addBook（）。设置setCustomerName（）和SetCustomerAddress（）的getters和setter后，我在测试类中没有错误。我的问题是，如何在Order类中创建5个Book实例变量，如果它们被调用（从带有addBook（）的Test类），将被填充Test对象中创建的Book对象的成员数据（或参数）以便我可以在同一个类中的其他方法中使用它们。例如，在类Test中，如果我调用addBook（b1），Order类中的addBook（）方法应该初始化或填充Book实例变量之一我想这是一个对象？）在Order中创建，并且Test类中引用的成员数据（带有b＃1-5）。这两个班。我没有把书类，因为它只是创建书籍对象。很感谢任何形式的帮助！

import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 

public class Test 
{ 
public static void main(String args[]) throws ParseException 
{ 
    SimpleDateFormat fmt = new SimpleDateFormat(Book.DATE_FORMAT); 

    // Creating Book-objects... 
    Book b1 = new Book(1, "Homo Faber", "Max Frisch", fmt.parse("01.01.1957"), -10); 
    Book b2 = new Book(2, "Harry Potter", "J.K. Rowling", fmt.parse("25.7.2000"), 45); 
    Book b3 = new Book(3, "Krieg und Frieden", "Leo Tolstoi", fmt.parse("24.01.1867"), 29); 
    Book b4 = new Book(4, "Freedom", "Jonathan Franzen", fmt.parse("08.06.2010"), 39); 
    Book b5 = new Book(5, "Goedel, Escher, Bach", "Douglas Hofstadter", fmt.parse("05.11.1979"),  42); 

    // Creating two orders containing theses books... 

    Order order = new Order(); 
    order.setCustomerName("Sophie Muster"); 
    order.setCustomerAddress("Mittelstrasse 10, 3011 Bern"); 
    order.addBook(b1);//Here i want to fill one of the Book instance variables (i guess this is  an object to?) created 
    order.addBook(b2);//in the Order class with the member data of the 
    order.addBook(b3);//Book objects referenced (with b#1-5) which i have created above. 
    order.addBook(b4); 
    order.addBook(b4); 
    order.addBook(b5); 
    System.out.println(order); 

    System.out.print("\n"); 

    Order order2 = new Order(); 
    order2.setCustomerName("Woody Allen"); 
    order2.setCustomerAddress("5th Avenue 7, 10001 New York"); 
    order2.addBook(b5); 
    System.out.println(order2); 
} 
} 

。

public class Order { 

private static int idCounter; 
private int id; 
private String customerName; 
private String customerAddress; 



// The Constructor 
public Order(int tmpId, String tmpCustomerName,String tmpCustomerAddress){ 
    if (idCounter == 1);{ 
     id = 1;} 
    if (idCounter == 2){ 
     id = 2;} 
    if (idCounter == 3);{ 
     id = 3;} 
    if (idCounter == 4){ 
     id = 4;} 
    if (idCounter == 5){ 
     id = 5;} 
    customerName = tmpCustomerName; 
    customerAddress = tmpCustomerAddress; 
    } 

public Order() { 
    id = 0; 
    customerName = "-"; 
    customerAddress = "-"; 
} 

// The methods 
public String toString() 
{ 
    return id + ", " + customerName + ", " + customerAddress; 
} 

public String addBook(){ 
    //HERE with this method i want to add some of the Book objects i have made in Test class 
    // ?? Book b1 = Test.b1(); ?? 

    return "0"; 

} 

public int getTotalPrice(){ 
    return 0; 

} 
public String getCustomerName() 
{ 
    return customerName; 
} 
public String setCustomerName(String tmpCustomerName){ 
    customerName = tmpCustomerName; 
    return customerName; 
} 
public String getCustomerAddress() 
{ 
    return customerAddress; 
} 
public String setCustomerAddress(String tmpCustomerAddress){ 
    customerAddress = tmpCustomerAddress; 
    return customerAddress; 
} 
} 

Answer 1

您可以在类中添加一个列表Order，类似于

private List<Book> books = new ArrayList<Book>(); 

你的方法可能是这样的：

public String addBook(Book book){ 
    books.add(book); 
    return "Book added"; 
} 

所以，你可以处理，添加，删除，更新书籍在您的订单！

Answer 2

您应该简单地增加一个List<Book>在Order和初始化：

public class Order { 

    List<Book> books = new ArrayList<>(); 

    public String addBook(Book book){ 
     books.add(book); 
     return "0"; 
    } 

    ... 
} 

然后你只需在顺序类迭代books拿到总价格，转换为字符串，...