用Java写一份复杂的图书管理系统

一个完整的图书管理系统需要包括图书的分类管理、图书借阅管理、读者管理、图书馆管理等多个方面的功能。下面是一个简单的Java代码示例，包含了图书分类、图书借阅和读者管理三个模块的实现。

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Scanner;

public class LibraryManagementSystem {
    private HashMap<String, ArrayList<Book>> bookMap;
    private ArrayList<BorrowRecord> borrowRecordList;
    private ArrayList<Reader> readerList;

    public LibraryManagementSystem() {
        bookMap = new HashMap<String, ArrayList<Book>>();
        borrowRecordList = new ArrayList<BorrowRecord>();
        readerList = new ArrayList<Reader>();
    }

    public void addBook(Book book) {
        String category = book.getCategory();
        if (!bookMap.containsKey(category)) {
            bookMap.put(category, new ArrayList<Book>());
        }
        bookMap.get(category).add(book);
    }

    public ArrayList<Book> findBookByCategory(String category) {
        if (!bookMap.containsKey(category)) {
            return new ArrayList<Book>();
        }
        return bookMap.get(category);
    }

    public void borrowBook(Book book, Reader reader) throws Exception {
        if (book.getStatus() == Book.Status.BORROWED) {
            throw new Exception("该图书已被借出！");
        }
        book.setStatus(Book.Status.BORROWED);
        BorrowRecord borrowRecord = new BorrowRecord(book, reader, new Date());
        borrowRecordList.add(borrowRecord);
    }

    public void returnBook(Book book, Reader reader) throws Exception {
        BorrowRecord borrowRecord = null;
        for (BorrowRecord record : borrowRecordList) {
            if (record.getBook() == book && record.getReader() == reader) {
                borrowRecord = record;
                break;
            }
        }
        if (borrowRecord == null) {
            throw new Exception("未找到该借阅记录！");
        }
        if (borrowRecord.getReturnDate() != null) {
            throw new Exception("该图书已归还！");
        }
        borrowRecord.setReturnDate(new Date());
        book.setStatus(Book.Status.AVAILABLE);
    }

    public void addReader(Reader reader) {
        readerList.add(reader);
    }

    public Reader findReader(String id) {
        for (Reader reader : readerList) {
            if (reader.getId().equals(id)) {
                return reader;
            }
        }
        return null;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        LibraryManagementSystem libraryManagementSystem = new LibraryManagementSystem();

        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1.添加图书");
            System.out.println("2.查找图书");
            System.out.println("3.借出图书");
            System.out.println("4.归还图书");
            System.out.println("5.添加读者");
            System.out.println("6.查找读者");
            System.out.println("7.退出");

            int choice = scanner.nextInt();

            if (choice == 1) {
                System.out.println("请输入图书的标题、作者和分类：");
                String title = scanner.next();
                String author = scanner.next();
                String category = scanner.next();
                Book book = new Book(title, author, category);
                libraryManagementSystem.addBook(book);
                System.out.println("添加成功！");
            } else if (choice == 2) {
                System.out.println("请输入要查找的图书的分类：");
                String category = scanner.next();
                ArrayList<Book> bookList = libraryManagementSystem.findBookByCategory(category);
                System.out.println("找到 " + bookList.size() + " 本图书：");
                for (Book book : bookList) {
                    System.out.println(book);
                }
            } else if (choice == 3) {
                System.out.println("请输入要借阅的图书的标题和作者：");
                String title = scanner.next();
                String author = scanner.next();
                Book book = null;
                for (ArrayList<Book> list : libraryManagementSystem.bookMap.values()) {
                    for (Book b : list) {
                        if (b.getTitle().equals(title) && b.getAuthor().equals(author)) {
                            book = b;
                            break;
                        }
                    }
                    if (book != null) {
                        break;
                    }
                }
                if (book == null) {
                    System.out.println("未找到该图书！");
                    continue;
                }
                System.out.println("请输入借阅人的ID：");
                String readerId = scanner.next();
                Reader reader = libraryManagementSystem.findReader(readerId);
                if (reader == null) {
                    System.out.println("未找到该读者！");
                    continue;
                }
                try {
                    libraryManagementSystem.borrowBook(book, reader);
                    System.out.println("借阅成功！");
                } catch (Exception e) {
                    System.out.println(e.getMessage());
                }
            } else if (choice == 4) {
                System.out.println("请输入要归还的图书的标题和作者：");
                String title = scanner.next();
                String author = scanner.next();
                Book book = null;
                for (ArrayList<Book> list : libraryManagementSystem.bookMap.values()) {
                    for (Book b : list) {
                        if (b.getTitle().equals(title) && b.getAuthor().equals(author)) {
                            book = b;
                            break;
                        }
                    }
                    if (book != null) {
                        break;
                    }
                }
                if (book == null) {
                    System.out.println("未找到该图书！");
                    continue;
                }
                System.out.println("请输入归还人的ID：");
                String readerId = scanner.next();
                Reader reader = libraryManagementSystem.findReader(readerId);
                if (reader == null) {
                    System.out.println("未找到该读者！");
                    continue;
                }
                try {
                    libraryManagementSystem.returnBook(book, reader);
                    System.out.println("归还成功！");
                } catch (Exception e) {
                    System.out.println(e.getMessage());
                }
            } else if (choice == 5) {
                System.out.println("请输入读者的ID和姓名：");
                String id = scanner.next();
                String name = scanner.next();
                Reader reader = new Reader(id, name);
                libraryManagementSystem.addReader(reader);
                System.out.println("添加成功！");
            } else if (choice == 6) {
                System.out.println("请输入要查找的读者的ID：");
                String id = scanner.next();
                Reader reader = libraryManagementSystem.findReader(id);
                if (reader == null) {
                    System.out.println("未找到该读者！");
                } else {
                    System.out.println(reader);
                }
            } else if (choice == 7) {
                System.out.println("感谢使用图书馆管理系统！");
                break;
            } else {
                System.out.println("输入错误，请重新输入！");
            }
        }
    }
}

class Book {
    private String title;
    private String author;
    private String category;
    private Book.Status status;

    public Book(String title, String author, String category) {
        this.title = title;
        this.author = author;
        this.category = category;
        this.status = Book.Status.AVAILABLE;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public String getCategory() {
        return category;
    }

    public Book.Status getStatus() {
        return status;
    }

    public void setStatus(Book.Status status) {
        this.status = status;
    }

    public String toString() {
        return "《" + title + "》 作者：" + author + " 分类：" + category;
    }

    public enum Status {
        AVAILABLE,
        BORROWED
    }
}

class BorrowRecord {
    private Book book;
    private Reader reader;
    private Date borrowDate;
    private Date returnDate;

    public BorrowRecord(Book book, Reader reader, Date borrowDate) {
        this.book = book;
        this.reader = reader;
        this.borrowDate = borrowDate;
    }

    public Book getBook() {
        return book;
    }

    public Reader getReader() {
        return reader;
    }

    public Date getBorrowDate() {
        return borrowDate;
    }

    public Date getReturnDate() {
        return returnDate;
    }

    public void setReturnDate(Date returnDate) {
        this.returnDate = returnDate;
    }
}

class Reader {
    private String id;
    private String name;

    public Reader(String id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String toString() {
        return "读者ID：" + id + " 姓名：" + name;
    }
}

该程序实现了基本的图书分类、图书借阅和读者管理功能，包括添加图书、查找图书、借出图书、归还图书、添加读者、查找读者等。需要注意的是，该示例只是一个简单的示例，实际应用中可能需要更加完善的功能和界面设计。