定义两个类 Book, BookDAO, 其中Book类用于封装一个书籍对象，BookDAO中实现对于文本文件Book.txt的增加、修改、删除和查询方法（至少4种查询方法）

在面向对象编程中，我们可以创建两个类来分别处理书籍的对象和数据库操作。这里是一个简单的示例，使用Python来实现这个场景：

class Book:
    def __init__(self, title, author, id=None):
        self.title = title
        self.author = author
        self.id = id

    def __str__(self):
        return f"ID: {self.id}, Title: {self.title}, Author: {self.author}"

class BookDAO:
    def __init__(self, filename="Book.txt"):
        self.filepath = filename
        self.data = {}  # 初始时假设数据存储在一个字典中，实际应用可能需要读取文件或数据库初始化

    # 增加方法
    def add_book(self, book):
        book.id = len(self.data) + 1
        self.data[book.id] = book
        with open(self.filepath, 'a') as file:
            file.write(f"{book}\n")

    # 修改方法
    def update_book(self, book_id, updated_book):
        if book_id in self.data:
            self.data[book_id] = updated_book
            with open(self.filepath, 'w') as file:
                for id_, book in self.data.items():
                    file.write(str(book))
                    file.write("\n")
        else:
            print("Book not found.")

    # 删除方法
    def delete_book(self, book_id):
        if book_id in self.data:
            del self.data[book_id]
            with open(self.filepath, 'w') as file:
                for id_, book in self.data.items():
                    file.write(str(book))
                    file.write("\n")
        else:
            print("Book not found.")

    # 查询方法
    def get_book_by_id(self, book_id):
        if book_id in self.data:
            return self.data.get(book_id)
        else:
            return None

    def search_by_title(self, title):
        return [book for book in self.data.values() if book.title == title]

    def search_by_author(self, author):
        return [book for book in self.data.values() if book.author == author]

# 使用示例
book1 = Book("Python Crash Course", "Eric Matthes")
bookDAO = BookDAO()
bookDAO.add_book(book1)
print(bookDAO.get_book_by_id(1))  # 查找id为1的书
books_by_title = bookDAO.search_by_title("Python Crash Course")  # 搜索标题包含"Python Crash Course"的书

在这个例子中，`Book`类代表单个书籍对象，而`BookDAO`类包含了针对`Book.txt`文件的操作方法，包括添加、更新、删除和各种查询方法。