public Date getPubdate() { return pubdate; }

根据代码中的实现来看，`getPubdate()` 是一个Java类中的公有方法（public method），用于获取该类中私有成员变量 `pubdate` 的值。由于方法返回值类型为 `Date`，因此可以猜测 `pubdate` 可能是一个日期类型的变量。该方法的作用是返回 `pubdate` 的值，供其他代码使用。

相关问题

使用注解的方式，实现对虚拟数据表 news(id(int),title(varcha(100)),author(varchar(50)),content(text),pubdate(date)) 进行操作的三层结构，写出测试程序

注解方式的三层结构包括：实体类、数据访问层（DAO）、业务逻辑层（Service）。以下是对应的代码示例：

实体类 News：

public class News {
    private int id;
    private String title;
    private String author;
    private String content;
    private Date pubdate;

    public News() {}

    public News(int id, String title, String author, String content, Date pubdate) {
        this.id = id;
        this.title = title;
        this.author = author;
        this.content = content;
        this.pubdate = pubdate;
    }

    // getter and setter methods
}

数据访问层 NewsDAO：

public interface NewsDAO {
    @Select("SELECT * FROM news WHERE id=#{id}")
    News findById(int id);

    @Select("SELECT * FROM news ORDER BY pubdate DESC")
    List<News> findAll();

    @Insert("INSERT INTO news (title, author, content, pubdate) VALUES (#{title}, #{author}, #{content}, #{pubdate})")
    int addNews(News news);

    @Update("UPDATE news SET title=#{title}, author=#{author}, content=#{content}, pubdate=#{pubdate} WHERE id=#{id}")
    int updateNews(News news);

    @Delete("DELETE FROM news WHERE id=#{id}")
    int deleteNews(int id);
}

业务逻辑层 NewsService：

@Service
public class NewsService {
    @Autowired
    private NewsDAO newsDAO;

    public News getNewsById(int id) {
        return newsDAO.findById(id);
    }

    public List<News> getAllNews() {
        return newsDAO.findAll();
    }

    public void addNews(News news) {
        newsDAO.addNews(news);
    }

    public void updateNews(News news) {
        newsDAO.updateNews(news);
    }

    public void deleteNews(int id) {
        newsDAO.deleteNews(id);
    }
}

测试程序 NewsTest：

@RunWith(SpringRunner.class)
@SpringBootTest
public class NewsTest {
    @Autowired
    private NewsService newsService;

    @Test
    public void testCRUD() {
        // 添加新闻
        News news = new News(1, "Java 从入门到精通", "张三", "Java 是一门很好的语言", new Date());
        newsService.addNews(news);
        assertThat(news.getId()).isGreaterThan(0);

        // 查询新闻
        News savedNews = newsService.getNewsById(news.getId());
        assertThat(savedNews.getTitle()).isEqualTo("Java 从入门到精通");

        // 更新新闻
        savedNews.setTitle("Java 从入门到放弃");
        newsService.updateNews(savedNews);
        News updatedNews = newsService.getNewsById(savedNews.getId());
        assertThat(updatedNews.getTitle()).isEqualTo("Java 从入门到放弃");

        // 删除新闻
        newsService.deleteNews(updatedNews.getId());
        News deletedNews = newsService.getNewsById(updatedNews.getId());
        assertThat(deletedNews).isNull();
    }
}

以上代码示例使用了 Spring Boot 和 MyBatis 框架，可根据实际情况进行调整。

用java实现图书借阅管理系统

图书借阅管理系统涉及到很多方面，包括图书、读者、借阅记录等等，因此需要设计多个实体类，还需要考虑到数据的持久化存储等问题。下面是一个简单的图书借阅管理系统的程序示例，供参考：

1.实体类设计

（1）图书类Book

public class Book {
    private String id;     //图书编号
    private String name;   //图书名称
    private String author; //作者
    private String pub;    //出版社
    private String pubDate;//出版日期
    private int status;    //借阅状态，0表示未借出，1表示已借出

    public Book(){}

    public Book(String id, String name, String author, String pub, String pubDate, int status) {
        this.id = id;
        this.name = name;
        this.author = author;
        this.pub = pub;
        this.pubDate = pubDate;
        this.status = status;
    }

    //getters and setters
    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 getPub() {
        return pub;
    }

    public void setPub(String pub) {
        this.pub = pub;
    }

    public String getPubDate() {
        return pubDate;
    }

    public void setPubDate(String pubDate) {
        this.pubDate = pubDate;
    }

    public int getStatus() {
        return status;
    }

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

（2）读者类Reader

public class Reader {
    private String id;       //读者编号
    private String name;     //读者姓名
    private String phoneNum; //联系电话
    private String email;    //电子邮件
    private int maxNum;      //最多借阅数量
    private int borrowNum;   //已借阅数量

    public Reader(){}

    public Reader(String id, String name, String phoneNum, String email, int maxNum, int borrowNum) {
        this.id = id;
        this.name = name;
        this.phoneNum = phoneNum;
        this.email = email;
        this.maxNum = maxNum;
        this.borrowNum = borrowNum;
    }

    //getters and setters
    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 getPhoneNum() {
        return phoneNum;
    }

    public void setPhoneNum(String phoneNum) {
        this.phoneNum = phoneNum;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getMaxNum() {
        return maxNum;
    }

    public void setMaxNum(int maxNum) {
        this.maxNum = maxNum;
    }

    public int getBorrowNum() {
        return borrowNum;
    }

    public void setBorrowNum(int borrowNum) {
        this.borrowNum = borrowNum;
    }
}

（3）借阅记录类BorrowRecord

public class BorrowRecord {
    private String id;         //借阅记录编号
    private String bookId;     //图书编号
    private String readerId;   //读者编号
    private String borrowDate; //借阅日期
    private String returnDate; //归还日期
    private int renewTimes;    //续借次数

    public BorrowRecord(){}

    public BorrowRecord(String id, String bookId, String readerId, String borrowDate, String returnDate, int renewTimes) {
        this.id = id;
        this.bookId = bookId;
        this.readerId = readerId;
        this.borrowDate = borrowDate;
        this.returnDate = returnDate;
        this.renewTimes = renewTimes;
    }

    //getters and setters
    public String getId() {
        return id;
    }

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

    public String getBookId() {
        return bookId;
    }

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

    public String getReaderId() {
        return readerId;
    }

    public void setReaderId(String readerId) {
        this.readerId = readerId;
    }

    public String getBorrowDate() {
        return borrowDate;
    }

    public void setBorrowDate(String borrowDate) {
        this.borrowDate = borrowDate;
    }

    public String getReturnDate() {
        return returnDate;
    }

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

    public int getRenewTimes() {
        return renewTimes;
    }

    public void setRenewTimes(int renewTimes) {
        this.renewTimes = renewTimes;
    }
}

2.数据存储设计

这里使用MySQL数据库作为数据存储，需要新建三个表分别存储图书、读者和借阅记录。下面是三个表的SQL语句：

（1）图书表books

CREATE TABLE `books` (
  `id` varchar(50) NOT NULL,
  `name` varchar(100) NOT NULL,
  `author` varchar(100) NOT NULL,
  `pub` varchar(100) NOT NULL,
  `pubDate` varchar(20) NOT NULL,
  `status` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

（2）读者表readers

CREATE TABLE `readers` (
  `id` varchar(50) NOT NULL,
  `name` varchar(50) NOT NULL,
  `phoneNum` varchar(20) NOT NULL,
  `email` varchar(50) NOT NULL,
  `maxNum` int(11) NOT NULL DEFAULT '5',
  `borrowNum` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

（3）借阅记录表borrow_records

CREATE TABLE `borrow_records` (
  `id` varchar(50) NOT NULL,
  `bookId` varchar(50) NOT NULL,
  `readerId` varchar(50) NOT NULL,
  `borrowDate` varchar(20) NOT NULL,
  `returnDate` varchar(20) DEFAULT NULL,
  `renewTimes` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

3.程序实现

（1）添加图书

public void addBook(Book book){
    try {
        Connection conn = DBUtil.getConnection();
        String sql = "insert into books(id, name, author, pub, pubDate) values(?,?,?,?,?)";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, book.getId());
        ps.setString(2, book.getName());
        ps.setString(3, book.getAuthor());
        ps.setString(4, book.getPub());
        ps.setString(5, book.getPubDate());
        ps.executeUpdate();
        ps.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

（2）删除图书

public void deleteBook(String id){
    try {
        Connection conn = DBUtil.getConnection();
        String sql = "delete from books where id=?";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, id);
        ps.executeUpdate();
        ps.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

（3）修改图书信息

public void updateBook(Book book){
    try {
        Connection conn = DBUtil.getConnection();
        String sql = "update books set name=?, author=?, pub=?, pubDate=?, status=? where id=?";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, book.getName());
        ps.setString(2, book.getAuthor());
        ps.setString(3, book.getPub());
        ps.setString(4, book.getPubDate());
        ps.setInt(5, book.getStatus());
        ps.setString(6, book.getId());
        ps.executeUpdate();
        ps.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

（4）查询图书信息

public List<Book> queryBooks(){
    List<Book> books = new ArrayList<>();
    try {
        Connection conn = DBUtil.getConnection();
        String sql = "select * from books";
        PreparedStatement ps = conn.prepareStatement(sql);
        ResultSet rs = ps.executeQuery();
        while(rs.next()){
            Book book = new Book();
            book.setId(rs.getString("id"));
            book.setName(rs.getString("name"));
            book.setAuthor(rs.getString("author"));
            book.setPub(rs.getString("pub"));
            book.setPubDate(rs.getString("pubDate"));
            book.setStatus(rs.getInt("status"));
            books.add(book);
        }
        rs.close();
        ps.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return books;
}

（5）借阅图书

public void borrowBook(String bookId, String readerId){
    try {
        Connection conn = DBUtil.getConnection();
        //判断该图书是否已经借出
        String sql1 = "select status from books where id=?";
        PreparedStatement ps1 = conn.prepareStatement(sql1);
        ps1.setString(1, bookId);
        ResultSet rs1 = ps1.executeQuery();
        int status = 0;
        if(rs1.next()){
            status = rs1.getInt("status");
        }
        if(status == 1){
            System.out.println("该图书已经借出！");
            return;
        }
        //判断该读者是否还能借阅
        String sql2 = "select maxNum, borrowNum from readers where id=?";
        PreparedStatement ps2 = conn.prepareStatement(sql2);
        ps2.setString(1, readerId);
        ResultSet rs2 = ps2.executeQuery();
        int maxNum = 0;
        int borrowNum = 0;
        if(rs2.next()){
            maxNum = rs2.getInt("maxNum");
            borrowNum = rs2.getInt("borrowNum");
        }
        if(borrowNum >= maxNum){
            System.out.println("该读者已经达到最大借阅数量！");
            return;
        }
        //更新图书状态和读者借阅数量
        String sql3 = "update books set status=1 where id=?";
        PreparedStatement ps3 = conn.prepareStatement(sql3);
        ps3.setString(1, bookId);
        ps3.executeUpdate();
        String sql4 = "update readers set borrowNum=borrowNum+1 where id=?";
        PreparedStatement ps4 = conn.prepareStatement(sql4);
        ps4.setString(1, readerId);
        ps4.executeUpdate();
        //添加借阅记录
        String id = UUID.randomUUID().toString();
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String borrowDate = sdf.format(date);
        String sql5 = "insert into borrow_records(id, bookId, readerId, borrowDate) values(?,?,?,?)";
        PreparedStatement ps5 = conn.prepareStatement(sql5);
        ps5.setString(1, id);
        ps5.setString(2, bookId);
        ps5.setString(3, readerId);
        ps5.setString(4, borrowDate);
        ps5.executeUpdate();
        rs1.close();
        ps1.close();
        rs2.close();
        ps2.close();
        ps3.close();
        ps4.close();
        ps5.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

（6）归还图书

public void returnBook(String bookId, String readerId){
    try {
        Connection conn = DBUtil.getConnection();
        //判断该图书是否已经借出
        String sql1 = "select status from books where id=?";
        PreparedStatement ps1 = conn.prepareStatement(sql1);
        ps1.setString(1, bookId);
        ResultSet rs1 = ps1.executeQuery();
        int status = 0;
        if(rs1.next()){
            status = rs1.getInt("status");
        }
        if(status == 0){
            System.out.println("该图书未借出！");
            return;
        }
        //更新图书状态和读者借阅数量
        String sql2 = "update books set status=0 where id=?";
        PreparedStatement ps2 = conn.prepareStatement(sql2);
        ps2.setString(1, bookId);
        ps2.executeUpdate();
        String sql3 = "update readers set borrowNum=borrowNum-1 where id=?";
        PreparedStatement ps3 = conn.prepareStatement(sql3);
        ps3.setString(1, readerId);
        ps3.executeUpdate();
        //更新借阅记录
        String sql4 = "update borrow_records set returnDate=? where bookId=? and readerId=? and returnDate is null";
        PreparedStatement ps4 = conn.prepareStatement(sql4);
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String returnDate = sdf.format(date);
        ps4.setString(1, returnDate);
        ps4.setString(2, bookId);
        ps4.setString(3, readerId);
        ps4.executeUpdate();
        //计算罚款金额
        String sql5 = "select id, borrowDate, returnDate from borrow_records where bookId=? and readerId=? and returnDate is not null";
        PreparedStatement ps5 = conn.prepareStatement(sql5);
        ps5.setString(1, bookId);
        ps5.setString(2, readerId);
        ResultSet rs5 = ps5.executeQuery();
        double fine = 0.0;
        while(rs5.next()){
            String id = rs5.getString("id");
            String borrowDate = rs5.getString("borrowDate");
            String returnDate = rs5.getString("returnDate");
            long days = (sdf.parse(returnDate).getTime() - sdf.parse(borrowDate).getTime()) / (24 * 60 * 60 * 1000);
            if(days > 30){
                fine += (days - 30) * 0.1;
            }
        }
        if(fine > 0){
            System.out.println("该读者需要缴纳罚款：" + fine + "元。");
        }
        rs1.close();
        ps1.close();
        ps2.close();
        ps3.close();
        ps4.close();
        rs5.close();
        ps5.close();
        conn.close();
    } catch (SQLException | ParseException e) {
        e.printStackTrace();
    }
}

（7）查询借阅记录

public List<BorrowRecord> queryBorrowRecords(){
    List<BorrowRecord> records = new ArrayList<>();
    try {
        Connection conn = DBUtil.getConnection();
        String sql = "select * from borrow_records";
        PreparedStatement ps = conn.prepareStatement(sql);
        ResultSet rs = ps.executeQuery();
        while(rs.next()){
            BorrowRecord record = new BorrowRecord();
            record.setId(rs.getString("id"));
            record.setBookId(rs.getString("bookId"));
            record.setReaderId(rs.getString("readerId"));
            record.setBorrowDate(rs.getString("borrowDate"));
            record.setReturnDate(rs.getString("returnDate"));
            record.setRenewTimes(rs.getInt("renewTimes"));
            records.add(record);
        }
        rs.close();
        ps.close();
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return records;
}

以上是一个简单的图书借阅管理系统的程序示例，实际应用中还需要考虑到很多细节问题，比如图书和读者信息的修改和删除、借阅记录的续借和归还等等。