Java 对象库的方法问题

我正在尝试制作一个程序，创建一个不同书籍的库，我为库中的每个项目设置了一个副本数量，每次我签出一个项目时，我希望它仅从我签出的特定对象中扣除一个副本，但它会从所有对象中拿走一个副本。不知道如何解决这个问题

public abstract class Item{
  private int identify;
  private String title;
  private int copies;

  public Item(){
    identify=0;
    title="N/A";
    copies=0;
  }
  public Item(int id, int copy, String t){
    identify=id;
    copies=copy;
    title=t;
  }
  public void setIdentificationNumber(int id){
    identify = id;
  }
  public void setTitle(String t){
    title=t;
  }
  public void setNumberCopies(int num){
    copies=num;
  }
  public int getIdentificationNumber(){
    return identify;
  }
  public String getTitle(){
    return title;
  }
  public int getNumberCopies(){
    return copies;
  }
  public void checkOut(){
    if(copies>0){
      copies-=1;
      System.out.println("You have checked out "+title+". Thank You");
    }
    else{
      System.out.println("All copies of "+title+" are checked out!");
    }
  }
  public void checkIn(){
    copies+=1;
  }
}

问题也可能出在我的客户端方法中，我已经在下面发布了相应的代码

import java.util.Arrays;
import java.util.Scanner;
public class Library{
  static String title;
  static String author;
  static int id;
  static int copies;
  static String date;
  static Book[] database = new Book[100];
  static int count=0;

  public static void main(String[] args){
    int i;
    Scanner s = new Scanner(System.in);
    do{
      addBook();
      System.out.println("would you like to add another book?");
      i=s.nextInt();
    }while(i == 0);
    database[0].viewDetails();
    database[1].viewDetails();
    checkingOut();
    database[0].viewDetails();
    database[1].viewDetails();
  }
  public static void addBook(){
    Scanner s = new Scanner(System.in);
    System.out.println("Enter the title of the book you want to add to the collection");
    title=s.nextLine();
    System.out.println("Enter the author of the book you want to add to the collection");
    author=s.nextLine();
    System.out.println("Enter the publishing date of the book you want to add to the collection");
    date=s.nextLine();
    System.out.println("Enter the ID number of the book you want to add to the collection");
    id=s.nextInt();
    System.out.println("Enter the the number of copies that will be added into the collection");
    copies=s.nextInt();

    Book Book1 = new Book(date, author, copies, id, title);
    database[count] = Book1;
    count++;
  }
  public static void checkingOut(){
    boolean found=false;
    int idSearch;
    int i=0;
    Scanner s = new Scanner(System.in);
    System.out.println("Enter the ID number of the book you want to check out");
    idSearch=s.nextInt();
    while(i<database.length && found!=true){
      if(database[i].getIdentificationNumber() == idSearch){
        found = true;
      }
      i++;
    }
    if(found==true){
      database[i].checkOut();
      System.out.println("There are "+database[i].getNumberCopies()+" copies left");
    }
    else{System.out.println("There is no book with that ID number!");}
  }
}

---

任何帮助都将不胜感激。

我不能100%地从您的代码中看出，但我假设这本书扩展了这个项目。在这种情况下，请为Book构造函数尝试类似的方法

public class Book extends Item {
    String author;
    String date;

    public Book(String date, String author, int copies, int id, String title) {
        super(id, copies, title); // Item constructor matches this super() call
                                  // public Item(int id, int copy, String t)
        this.author = author;
        this.date = date;
    }
}

---

您希望这本书在项目中有相同的副本。因此，当您签出时，项目编号等于您从Book构造函数中输入的内容。如果您不将super放入构造函数中，您的项目副本将保持为0，并且您将始终获得System.out.println+title+的所有副本都已签出！；因为拷贝数永远不会超过0。如果你的书是这样的

public class Book extends Item {

    private String date;
    private String author;

    public Book() {
    }

    public Book(String date, String author, int copies, int id, String title) {
        super(id, copies, title);
        this.author = author;
        this.date = date;
    }

    void viewDetails() {
        System.out.println("date:" + date + " author:" + author + " copies:" + getNumberCopies() + " id:" + getIdentificationNumber() + " title:" + getTitle());
    }
}

那么，正如我所测试的，如果您在checkingOut方法中添加一个中断，那么您的代码应该可以正常工作

---

你应该加上休息；在这一行之后，found=true？书是否扩展项目？是的书是否扩展项目，我有上级、副本、标题；在这本书的构造器中，让我来纠正一下。您的基本问题是，您正在获取此输出System.out.PrintLn+的所有副本都已签出！；您已签出+title+，而不是这一个System.out.println。非常感谢。我说得对吗。或者还有其他问题吗？您想显示WrittenItem的一个片段，仅显示相关代码，包括构造函数。@Julien Kerr，不，您的书构造函数中没有superid、copies和title。您的书本构造函数有一个super5参数

public class Book extends Item {

    private String date;
    private String author;

    public Book() {
    }

    public Book(String date, String author, int copies, int id, String title) {
        super(id, copies, title);
        this.author = author;
        this.date = date;
    }

    void viewDetails() {
        System.out.println("date:" + date + " author:" + author + " copies:" + getNumberCopies() + " id:" + getIdentificationNumber() + " title:" + getTitle());
    }
}

public static void checkingOut() {
        boolean found = false;
        int idSearch;
        int i = 0;
        Scanner s = new Scanner(System.in);
        System.out.println("Enter the ID number of the book you want to check out");
        idSearch = s.nextInt();
        while (i < database.length && found != true) {
            if (database[i].getIdentificationNumber() == idSearch) {
                found = true;
                break; //add this
            }
            i++;
        }
        if (found == true) {
            database[i].checkOut();
            System.out.println("There are " + database[i].getNumberCopies() + " copies left");
        } else {
            System.out.println("There is no book with that ID number!");
        }
    }