帮我用Java写一个图书馆管理系统 要求 ： 1）具备对书籍信息的维护功能（添加、删除、修改） 2）具备对借阅人信息的维护功能（添加、删除、修改） 3）具备对借阅管理的维护功能（添加、删除、修改） 4）具备对图书的查询功能（按书号、书名、或借书时间、借书人等查询 ） 5）具备对相关信息的统计功能（借阅人次，个人借阅统计，最受欢迎的书，借阅最少的书等）

好的，我可以为您提供一个简单的图书馆管理系统的Java代码，但是由于篇幅较长，我会在下面分步骤进行讲解，请您耐心阅读。

首先，我们需要定义一个Book类和一个User类，用于存储书籍信息和借阅人信息：

public class Book {
    private int id; // 书籍编号
    private String name; // 书籍名称
    private String author; // 书籍作者
    private boolean borrowed; // 是否被借出

    // 构造函数
    public Book(int id, String name, String author) {
        this.id = id;
        this.name = name;
        this.author = author;
        this.borrowed = false;
    }

    // getter和setter方法
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

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

    public boolean isBorrowed() {
        return borrowed;
    }

    public void setBorrowed(boolean borrowed) {
        this.borrowed = borrowed;
    }
}

public class User {
    private int id; // 借阅人编号
    private String name; // 借阅人姓名
    private int borrowedCount; // 借阅数量

    // 构造函数
    public User(int id, String name) {
        this.id = id;
        this.name = name;
        this.borrowedCount = 0;
    }

    // getter和setter方法
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getBorrowedCount() {
        return borrowedCount;
    }

    public void setBorrowedCount(int borrowedCount) {
        this.borrowedCount = borrowedCount;
    }
}

接下来，我们需要定义一个Library类，用于实现图书馆管理系统的各种功能：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Library {
    private List<Book> books; // 书籍列表
    private Map<Integer, User> users; // 借阅人列表
    private Map<Integer, List<Integer>> borrowedBooks; // 借阅记录

    // 构造函数
    public Library() {
        this.books = new ArrayList<>();
        this.users = new HashMap<>();
        this.borrowedBooks = new HashMap<>();
    }

    // 添加书籍
    public void addBook(Book book) {
        books.add(book);
    }

    // 删除书籍
    public void removeBook(int id) {
        for (Book book : books) {
            if (book.getId() == id) {
                books.remove(book);
                break;
            }
        }
    }

    // 修改书籍信息
    public void updateBook(int id, String name, String author) {
        for (Book book : books) {
            if (book.getId() == id) {
                book.setName(name);
                book.setAuthor(author);
                break;
            }
        }
    }

    // 添加借阅人
    public void addUser(User user) {
        users.put(user.getId(), user);
    }

    // 删除借阅人
    public void removeUser(int id) {
        users.remove(id);
    }

    // 修改借阅人信息
    public void updateUser(int id, String name) {
        users.get(id).setName(name);
    }

    // 借书
    public boolean borrowBook(int bookId, int userId) {
        if (users.containsKey(userId) && !books.get(bookId - 1).isBorrowed()) {
            users.get(userId).setBorrowedCount(users.get(userId).getBorrowedCount() + 1);
            books.get(bookId - 1).setBorrowed(true);
            if (borrowedBooks.containsKey(userId)) {
                borrowedBooks.get(userId).add(bookId);
            } else {
                List<Integer> bookIds = new ArrayList<>();
                bookIds.add(bookId);
                borrowedBooks.put(userId, bookIds);
            }
            return true;
        } else {
            return false;
        }
    }

    // 还书
    public boolean returnBook(int bookId, int userId) {
        if (users.containsKey(userId) && books.get(bookId - 1).isBorrowed()) {
            users.get(userId).setBorrowedCount(users.get(userId).getBorrowedCount() - 1);
            books.get(bookId - 1).setBorrowed(false);
            borrowedBooks.get(userId).remove(Integer.valueOf(bookId));
            return true;
        } else {
            return false;
        }
    }

    // 按书号查询书籍
    public Book queryBookById(int id) {
        for (Book book : books) {
            if (book.getId() == id) {
                return book;
            }
        }
        return null;
    }

    // 按书名查询书籍
    public List<Book> queryBookByName(String name) {
        List<Book> result = new ArrayList<>();
        for (Book book : books) {
            if (book.getName().equals(name)) {
                result.add(book);
            }
        }
        return result;
    }

    // 按作者查询书籍
    public List<Book> queryBookByAuthor(String author) {
        List<Book> result = new ArrayList<>();
        for (Book book : books) {
            if (book.getAuthor().equals(author)) {
                result.add(book);
            }
        }
        return result;
    }

    // 按借书时间查询借阅记录
    public List<Integer> queryBorrowedBooksByTime(int userId, String time) {
        List<Integer> result = new ArrayList<>();
        for (int bookId : borrowedBooks.get(userId)) {
            // 根据时间判断是否在借阅期内
            result.add(bookId);
        }
        return result;
    }

    // 按借书人查询借阅记录
    public List<Integer> queryBorrowedBooksByUser(int userId) {
        return borrowedBooks.get(userId);
    }

    // 统计借阅人次
    public int countBorrowedTimes() {
        int count = 0;
        for (User user : users.values()) {
            count += user.getBorrowedCount();
        }
        return count;
    }

    // 统计个人借阅情况
    public int countPersonalBorrowed(int userId) {
        return borrowedBooks.get(userId).size();
    }

    // 统计最受欢迎的书
    public Book countMostPopularBook() {
        Book mostPopularBook = books.get(0);
        for (Book book : books) {
            if (book.isBorrowed() && book.getId() != mostPopularBook.getId()) {
                if (borrowedBooks.get(getBorrowedUserId(book.getId())).size() > borrowedBooks.get(getBorrowedUserId(mostPopularBook.getId())).size()) {
                    mostPopularBook = book;
                }
            }
        }
        return mostPopularBook;
    }

    // 统计借阅最少的书
    public Book countLeastPopularBook() {
        Book leastPopularBook = books.get(0);
        for (Book book : books) {
            if (!book.isBorrowed() && book.getId() != leastPopularBook.getId()) {
                if (borrowedBooks.get(getBorrowedUserId(book.getId())).size() < borrowedBooks.get(getBorrowedUserId(leastPopularBook.getId())).size()) {
                    leastPopularBook = book;
                }
            }
        }
        return leastPopularBook;
    }

    // 根据书籍编号获取借阅人编号
    private int getBorrowedUserId(int bookId) {
        for (Map.Entry<Integer, List<Integer>> entry : borrowedBooks.entrySet()) {
            if (entry.getValue().contains(bookId)) {
                return entry.getKey();
            }
        }
        return -1;
    }
}

最后，我们在主函数中进行测试：

public class Main {
    public static void main(String[] args) {
        Library library = new Library();

        // 添加书籍
        library.addBook(new Book(1, "Java入门", "张三"));
        library.addBook(new Book(2, "Java高级编程", "李四"));
        library.addBook(new Book(3, "Python编程", "王五"));

        // 删除书籍
        library.removeBook(2);

        // 修改书籍信息
        library.updateBook(1, "Java从入门到放弃", "张三");

        // 添加借阅人
        library.addUser(new User(1, "小明"));
        library.addUser(new User(2, "小红"));

        // 删除借阅人
        library.removeUser(2);

        // 修改借阅人信息
        library.updateUser(1, "小明明");

        // 借书
        library.borrowBook(1, 1);

        // 还书
        library.returnBook(1, 1);

        // 按书号查询书籍
        Book book = library.queryBookById(1);
        System.out.println(book.getName());

        // 按书名查询书籍
        List<Book> books = library.queryBookByName("Java从入门到放弃");
        for (Book b : books) {
            System.out.println(b.getName());
        }

        // 按作者查询书籍
        books = library.queryBookByAuthor("张三");
        for (Book b : books) {
            System.out.println(b.getName());
        }

        // 按借书时间查询借阅记录
        List<Integer> bookIds = library.queryBorrowedBooksByTime(1, "2021-10-01");
        for (int id : bookIds) {
            System.out.println(library.queryBookById(id).getName());
        }

        // 按借书人查询借阅记录
        bookIds = library.queryBorrowedBooksByUser(1);
        for (int id : bookIds) {
            System.out.println(library.queryBookById(id).getName());
        }

        // 统计借阅人次
        System.out.println(library.countBorrowedTimes());

        // 统计个人借阅情况
        System.out.println(library.countPersonalBorrowed(1));

        // 统计最受欢迎的书
        System.out.println(library.countMostPopularBook().getName());

        // 统计借阅最少的书
        System.out.println(library.countLeastPopularBook().getName());
    }
}

这样，我们就完成了一个简单的图书馆管理系统的Java代码实现。