帮我用Java写一个图书管理系统。要求：1.通过从键盘输入具备对书籍信息的维护功能（添加、删除、修改）2.通过从键盘输入具备对借阅人的信息维护功能（添加，删除修改）3.通过从键盘输入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、借书时间、借书人等查询）5具备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，以下是用Java实现的图书管理系统代码示例：

Book.java

public class Book {
    private String id;
    private String name;
    private String author;
    private String publisher;
    private String isbn;
    private String publishTime;
    private double price;
    private int totalNum;
    private int borrowedNum;

    public Book() {}

    public Book(String id, String name, String author, String publisher, String isbn, String publishTime, double price, int totalNum, int borrowedNum) {
        this.id = id;
        this.name = name;
        this.author = author;
        this.publisher = publisher;
        this.isbn = isbn;
        this.publishTime = publishTime;
        this.price = price;
        this.totalNum = totalNum;
        this.borrowedNum = borrowedNum;
    }

    // getter and setter methods

    public String getId() {
        return id;
    }

    public void setId(String 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 String getPublisher() {
        return publisher;
    }

    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }

    public String getIsbn() {
        return isbn;
    }

    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }

    public String getPublishTime() {
        return publishTime;
    }

    public void setPublishTime(String publishTime) {
        this.publishTime = publishTime;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getTotalNum() {
        return totalNum;
    }

    public void setTotalNum(int totalNum) {
        this.totalNum = totalNum;
    }

    public int getBorrowedNum() {
        return borrowedNum;
    }

    public void setBorrowedNum(int borrowedNum) {
        this.borrowedNum = borrowedNum;
    }

    // toString method

    @Override
    public String toString() {
        return "Book{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", publisher='" + publisher + '\'' +
                ", isbn='" + isbn + '\'' +
                ", publishTime='" + publishTime + '\'' +
                ", price=" + price +
                ", totalNum=" + totalNum +
                ", borrowedNum=" + borrowedNum +
                '}';
    }
}

Borrower.java

public class Borrower {
    private String id;
    private String name;
    private String gender;
    private String contact;

    public Borrower() {}

    public Borrower(String id, String name, String gender, String contact) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.contact = contact;
    }

    // getter and setter methods

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getContact() {
        return contact;
    }

    public void setContact(String contact) {
        this.contact = contact;
    }

    // toString method

    @Override
    public String toString() {
        return "Borrower{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", contact='" + contact + '\'' +
                '}';
    }
}

BorrowRecord.java

public class BorrowRecord {
    private String id;
    private String borrowTime;
    private String returnTime;
    private String borrowerId;
    private String bookId;

    public BorrowRecord() {}

    public BorrowRecord(String id, String borrowTime, String returnTime, String borrowerId, String bookId) {
        this.id = id;
        this.borrowTime = borrowTime;
        this.returnTime = returnTime;
        this.borrowerId = borrowerId;
        this.bookId = bookId;
    }

    // getter and setter methods

    public String getId() {
        return id;
    }

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

    public String getBorrowTime() {
        return borrowTime;
    }

    public void setBorrowTime(String borrowTime) {
        this.borrowTime = borrowTime;
    }

    public String getReturnTime() {
        return returnTime;
    }

    public void setReturnTime(String returnTime) {
        this.returnTime = returnTime;
    }

    public String getBorrowerId() {
        return borrowerId;
    }

    public void setBorrowerId(String borrowerId) {
        this.borrowerId = borrowerId;
    }

    public String getBookId() {
        return bookId;
    }

    public void setBookId(String bookId) {
        this.bookId = bookId;
    }

    // toString method

    @Override
    public String toString() {
        return "BorrowRecord{" +
                "id='" + id + '\'' +
                ", borrowTime='" + borrowTime + '\'' +
                ", returnTime='" + returnTime + '\'' +
                ", borrowerId='" + borrowerId + '\'' +
                ", bookId='" + bookId + '\'' +
                '}';
    }
}

LibrarySystem.java

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class LibrarySystem {
    private List<Book> books;
    private List<Borrower> borrowers;
    private List<BorrowRecord> borrowRecords;
    private Scanner scanner;

    public LibrarySystem() {
        this.books = new ArrayList<>();
        this.borrowers = new ArrayList<>();
        this.borrowRecords = new ArrayList<>();
        this.scanner = new Scanner(System.in);
    }

    public void start() {
        boolean isQuit = false;
        while (!isQuit) {
            System.out.println("欢迎使用图书管理系统，请输入对应数字选择操作：");
            System.out.println("1. 添加书籍信息");
            System.out.println("2. 删除书籍信息");
            System.out.println("3. 修改书籍信息");
            System.out.println("4. 添加借阅人信息");
            System.out.println("5. 删除借阅人信息");
            System.out.println("6. 修改借阅人信息");
            System.out.println("7. 添加借阅记录");
            System.out.println("8. 删除借阅记录");
            System.out.println("9. 修改借阅记录");
            System.out.println("10. 按书号查询图书信息");
            System.out.println("11. 按书名查询图书信息");
            System.out.println("12. 按借书时间查询图书信息");
            System.out.println("13. 按借书人查询图书信息");
            System.out.println("14. 统计借阅人次");
            System.out.println("15. 统计个人借阅情况");
            System.out.println("16. 统计最受欢迎的书");
            System.out.println("17. 统计借阅最少的书");
            System.out.println("18. 退出系统");
            int choice = scanner.nextInt();
            scanner.nextLine(); // consume the newline character
            switch (choice) {
                case 1:
                    addBook();
                    break;
                case 2:
                    deleteBook();
                    break;
                case 3:
                    modifyBook();
                    break;
                case 4:
                    addBorrower();
                    break;
                case 5:
                    deleteBorrower();
                    break;
                case 6:
                    modifyBorrower();
                    break;
                case 7:
                    addBorrowRecord();
                    break;
                case 8:
                    deleteBorrowRecord();
                    break;
                case 9:
                    modifyBorrowRecord();
                    break;
                case 10:
                    searchBookById();
                    break;
                case 11:
                    searchBookByName();
                    break;
                case 12:
                    searchBookByBorrowTime();
                    break;
                case 13:
                    searchBookByBorrower();
                    break;
                case 14:
                    countBorrowTimes();
                    break;
                case 15:
                    countPersonalBorrow();
                    break;
                case 16:
                    countPopularBook();
                    break;
                case 17:
                    countLeastPopularBook();
                    break;
                case 18:
                    isQuit = true;
                    break;
                default:
                    System.out.println("输入有误，请重新输入！");
                    break;
            }
        }
    }

    private void addBook() {
        System.out.println("请输入书籍信息：");
        System.out.print("书号：");
        String id = scanner.nextLine();
        System.out.print("书名：");
        String name = scanner.nextLine();
        System.out.print("作者：");
        String author = scanner.nextLine();
        System.out.print("出版社：");
        String publisher = scanner.nextLine();
        System.out.print("ISBN：");
        String isbn = scanner.nextLine();
        System.out.print("出版时间：");
        String publishTime = scanner.nextLine();
        System.out.print("价格：");
        double price = scanner.nextDouble();
        System.out.print("库存数量：");
        int totalNum = scanner.nextInt();
        System.out.print("借阅数量：");
        int borrowedNum = scanner.nextInt();
        scanner.nextLine(); // consume the newline character
        Book book = new Book(id, name, author, publisher, isbn, publishTime, price, totalNum, borrowedNum);
        books.add(book);
        System.out.println("添加成功！");
    }

    private void deleteBook() {
        System.out.println("请输入要删除的书籍ID或书名：");
        String input = scanner.nextLine();
        boolean isDeleted = false;
        for (Book book : books) {
            if (book.getId().equals(input) || book.getName().equals(input)) {
                books.remove(book);
                isDeleted = true;
                break;
            }
        }
        if (isDeleted) {
            System.out.println("删除成功！");
        } else {
            System.out.println("未找到该书籍！");
        }
    }

    private void modifyBook() {
        System.out.println("请输入要修改的书籍ID或书名：");
        String input = scanner.nextLine();
        boolean isModified = false;
        for (Book book : books) {
            if (book.getId().equals(input) || book.getName().equals(input)) {
                System.out.println("请输入修改后的书籍信息：");
                System.out.print("书号：");
                book.setId(scanner.nextLine());
                System.out.print("书名：");
                book.setName(scanner.nextLine());
                System.out.print("作者：");
                book.setAuthor(scanner.nextLine());
                System.out.print("出版社：");
                book.setPublisher(scanner.nextLine());
                System.out.print("ISBN：");
                book.setIsbn(scanner.nextLine());
                System.out.print("出版时间：");
                book.setPublishTime(scanner.nextLine());
                System.out.print("价格：");
                book.setPrice(scanner.nextDouble());
                System.out.print("库存数量：");
                book.setTotalNum(scanner.nextInt());
                System.out.print("借阅数量：");
                book.setBorrowedNum(scanner.nextInt());
                scanner.nextLine(); // consume the newline character
                isModified = true;
                break;
            }
        }
        if (isModified) {
            System.out.println("修改成功！");
        } else {
            System.out.println("未找到该书籍！");
        }
    }

    private void addBorrower() {
        System.out.println("请输入借阅人信息：");
        System.out.print("借阅人ID：");
        String id = scanner.nextLine();
        System.out.print("姓名：");
        String name = scanner.nextLine();
        System.out.print("性别：");
        String gender = scanner.nextLine();
        System.out.print("联系方式：");
        String contact = scanner.nextLine();
        Borrower borrower = new Borrower(id, name, gender, contact);
        borrowers.add(borrower);
        System.out.println("添加成功！");
    }

    private void deleteBorrower() {
        System.out.println("请输入要删除的借阅人ID或姓名：");
        String input = scanner.nextLine();
        boolean isDeleted = false;
        for (Borrower borrower : borrowers) {
            if (borrower.getId().equals(input) || borrower.getName().equals(input)) {
                borrowers.remove(borrower);
                isDeleted = true;
                break;
            }
        }
        if (isDeleted) {
            System.out.println("删除成功！");
        } else {
            System.out.println("未找到该借阅人！");
        }
    }

    private void modifyBorrower() {
        System.out.println("请输入要修改的借阅人ID或姓名：");
        String input = scanner.nextLine();
        boolean isModified = false;
        for (Borrower borrower : borrowers) {
            if (borrower.getId().equals(input) || borrower.getName().equals(input)) {
                System.out.println("请输入修改后的借阅人信息：");
                System.out.print("借阅人ID：");
                borrower.setId(scanner.nextLine());
                System.out.print("姓名：");
                borrower.setName(scanner.nextLine());
                System.out.print("性别：");
                borrower.setGender(scanner.nextLine());
                System.out.print("联系方式：");
                borrower.setContact(scanner.nextLine());
                isModified