我是java的新手，很抱歉我的代码中存在不一致/混淆。
我正在创建一个简单的库程序，其中一个要求是显示库中的所有书籍及其状态（进出）
例如：
远大前程：IN
Kite Runner：OUT
呼啸山庄：OUT
然而，如果我只是检查一本书，它会将所有书籍状态“更改为”“更改”而不仅仅是其中一本。所以例如我继续得到：
远大前程：OUT
Kite Runner：OUT
呼啸山庄：OUT
在我的书类中，我有状态设置器/ getter，以及一个ArrayList BookList来保存所有的库书。
static ArrayList <String> BookList = new ArrayList <String> ();
public static String getStatus(String book)
{
return status;
}
public static void setStatus(String newStatus)
{
status = newStatus;
}
以下是赞助类中检查书籍的方法。
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!----------");
}
}
如何才能使它只有数组列表中的指定书籍改变其状态？我试图创建不同的方法，但似乎不起作用：
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 :(
书籍课程：
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;
}
}
答案 0 :(得分：1)
对于你的getStatus方法，你使用的是静态变量，这意味着它在alll Book实例中是相同的，你不想要它，只需从Book中的变量和方法中删除所有静态应该工作。
答案 1 :(得分：1)
为了对您的＆＃34;库＆＃34;进行建模，您需要拥有图书的实例。将您的Book类视为定义书籍内容的蓝图。然后，您需要使用此蓝图来创建实际的Book对象。
保持简单，这是Book类的一个例子。它定义了一本具有标题和签出状态的书。
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");
}
}
你会创建这样的特定书籍：
Book greatExpectations = new Book("Great Expectations", false);
这会创建一本标题为＃34; Great Expectations＆＃34;的新书，但不会检出。 System.out.println(greatExpectations)会打印Great Expectations: OUT。
因此，要设置您的＆＃34;库＆＃34;，请创建一系列图书并将其添加到List：
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 标记为已签出，我需要做的就是循环浏览列表，查找我正在寻找的书，并更改其选中的内容出州：
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，我会看到只有 Catch-22 被标记为已签出：
System.out.println(library);
// prints:
// [Great Expectations: IN, Moby Dick: IN, Catch-22: OUT, The Great Gatsby: IN]
您的实现使用静态方法。静态方法不设置特定实例的值，而是设置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，而是所有书籍。这就是为什么当您尝试将图书设置为已签出时，它会将所有图书更新为已检出。