图书馆程序中图书的状态分配

Question

我是java的新手，对代码中的不一致/混乱感到非常抱歉。

我正在创建一个简单的图书馆程序，其中一个要求是显示图书馆中的所有书籍及其状态(无论在里面还是向外)。

例如：

远大期望： 风筝追逐者:出局 呼啸山庄:出去

但是，如果我只检查了一本书，它就会将所有的图书状态更改为" out“，而不是其中的一本。举个例子，我一直在想：

远大期望:出局 风筝追逐者:出局 呼啸山庄:出去

在我的图书类中，我有类似的状态设置器/getter，还有一个保存所有库书籍的ArrayList BookList。

static ArrayList <String> BookList = new ArrayList <String> ();

public static String getStatus(String book)
    {
        return status; 
    }

  public static void setStatus(String newStatus)    
    {
        status = newStatus; 
    }

这是赞助类的借阅书籍的方法。

public static void CheckOutBook() 
{
      Scanner inputread = new Scanner(System.in);
      Scanner input = new Scanner(System.in);
      System.out.println("Enter full patron name: ");
      String borrower = inputread.nextLine();
      System.out.println("Enter book title to check out: ");
      String bookCheckOut = inputread.nextLine();

      if (Book.BookList.contains(bookCheckOut)) 
      {
        Book.BookList.remove(bookCheckOut);
        Book.setStatus("OUT");                   //?? doesnt work ??
        int bookIndex = Book.getIndexNumber(bookCheckOut);
        Book.setTrue(Book.BookList.get(bookIndex));
        Book.setBook(Book.BookList.get(bookIndex));
        Book.setBorrower(borrower);
        Book.setBook(bookCheckOut);
        System.out.println("----------" + bookCheckOut + " has been checked out!----------");

      }
}

如何才能使数组列表中只有指定的书籍更改其状态？我试图创建不同的方法，但这似乎也不起作用：

Book.setTrue(bookCheckOut);              //true if book checked out
Book.BookList.get(indexNum).setTrue(bookCheckOut);
Book.setTrue(Book.BookList.get(i));

//here are some of the other attemps ive tried but they still dont change anything :(

图书班：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Book implements BookInterface {
  Scanner input = new Scanner(System.in);

  static ArrayList < String > UserList = new ArrayList < String > ();
  static ArrayList < String > BookList = new ArrayList < String > (); //display just titles// use when checking out books
  static ArrayList < String > OrigBookList = new ArrayList < String > (); //keep track of all titles ever entered

  public static String title;
  public String author;
  public static String book;
  public boolean checkIn;

  public static String status;
  public static String borrower;


  public Book(String t, String a) {
    title = t;
    author = a;
  }


  //constructor create new book
  public Book(String newTitle) {
    title = newTitle;
  }


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

  public String getTitle() {
    return title;
  }

  public void setTitle(String title) {
    this.title = title;
  }

  public String getAuthor() {
    return author;
  }

  public void setAuthor(String author) {
    this.author = author;
  }

   public static String getStatus(String book) {
    return status;
  }

  public static void setStatus(String newStatus) 
    {
      status = newStatus;


  /**public static void setStatus(String newStatus)
    {
        status = newStatus; 
    }**/

  public static void setTrue(String bookCheckOut) {
    //status = true; 
  }

  public static void setFalse(String bookCheckIn) {
    //status = false; 
  }

  public static void setBorrower(String newBorrower) {
    borrower = newBorrower;
  }

  public static String getBorrower(String checkPatron) {
    return borrower;
  }

  public static String getBook(String checkPatron) {
    return book;
  }

  public static void setBook(String newBook) {
    book = newBook;
  }

  public static void addBook() {
    Scanner input = new Scanner(System.in);
    Scanner inputread = new Scanner(System.in);
    System.out.print("Enter book title: ");

    String title1 = inputread.nextLine();

    Scanner input1 = new Scanner(System.in);
    System.out.print("Enter book author: ");
    String author1 = inputread.next();

    Book fullBook = new Book(title1, author1); //create constructor w/ title & author
    Book book1 = new Book(title1); //constructor w/ just title to be used to display all books
    BookList.add(title1);
    OrigBookList.add(title1);
    //setStatus("IN");  //false = checked in 
    setFalse(title1);
    System.out.println("-----------------------------------------------");
    System.out.println("-----" + title1 + " is now in the library!-----");
    System.out.println("-----------------------------------------------");
  }

  public static void editBook() {
    Scanner inputread = new Scanner(System.in);
    System.out.println("Enter original book title: ");
    String origTitle = inputread.nextLine();
    System.out.println("Enter edited book title: ");
    String editedTitle = inputread.nextLine();
    Collections.replaceAll(Book.UserList, origTitle, editedTitle);
    System.out.println("------------------------------------------------------");
    System.out.println(origTitle + " has been changed to " + editedTitle + "!");
    System.out.println("------------------------------------------------------");

  }


  //print out list of books & if checked in or out
  public static void libraryInventory() {
    for (int i = 0; i <= OrigBookList.size() - 1; i++) {
      //Book Title: checked in/out
      System.out.println(OrigBookList.get(i) + ":" + getStatus(OrigBookList.get(i)));
    }
  }

  //method to go through BookList array and get index number for specifed 
  //book user has entered to check in/out 
  public static int getIndexNumber(String bookCheckOut) {
    int bookIndex = 0;
    for (int i = 0; i <= BookList.size() - 1; i++) {
      if (BookList.get(i).equals(bookCheckOut)) {
        bookIndex = i;
      }

    }
    return bookIndex;

  }

}

Answer 1

对于您的getStatus方法来说，您使用的是一个静态变量，这意味着它在所有图书实例中都是相同的，您不希望这样，只需从Book中的变量和方法中删除所有的静态变量，它就会正常工作。

Answer 2

为了建模您的“库”，您需要有图书的实例。将您的Book类看作是定义书籍的蓝图。然后，您需要使用此蓝图来创建实际的Book对象。

保持简单，这里是一个Book类的例子。它定义了一个具有标题和签出状态的图书。

public class Book {
  private String title;
  private boolean isCheckedOut;
  public Book(String title, boolean isCheckedOut) {
    this.title = title;
    this.isCheckedOut = isCheckdOut;
  }

  public void setTitle(String title) {
    this.title = title;
  }
  public String getTitle() {
    return title;
  }
  public void setCheckedOut(boolean isCheckedOut) {
    this.isCheckedOut = isCheckedOut;
  }
  public boolan isCheckedOut() {
    return isCheckedOut;
  }
  @Override
  public String toString() {
    return title + ": " + (isCheckedOut ? "OUT" : "IN");
  }
}

您可以创建这样的特定书籍：

Book greatExpectations = new Book("Great Expectations", false);

这就创建了一本名为“远大期望”的新书，而这本书并没有被检出。System.out.println(greatExpectations)会打印Great Expectations: OUT。

因此，为了设置您的“库”，让我们创建一个图书集合并将它们添加到List中

List<Book> library = new ArrayList<>();
library.add(new Book("Great Expectations", false));
library.add(new Book("Moby Dick", false));
library.add(new Book("Catch-22", false));
library.add(new Book("The Great Gatsby", false));

现在，如果我想将Catch-22标记为签出，我所需要做的就是遍历列表，找到我要查找的书，并更改其签出状态：

for(Book book : library) {
  if("Catch-22".equals(book.getTitle()) {
    book.setCheckedOut(true);
    break; // found the book, break out of the loop
  }
}

如果我现在打印出library的内容，我将看到只有Catch-22被标记为被签出：

System.out.println(library);

// prints:
// [Great Expectations: IN, Moby Dick: IN, Catch-22: OUT, The Great Gatsby: IN]

您的实现是使用静态方法。静态方法并不设置特定实例的值，而是在所有实例之间共享的值。

因此，就book类而言，静态方法不是为特定书籍设置属性，而是为所有书籍设置属性。这就是为什么当你试图将一本书设置为被结帐时，它会更新所有的书。