java代码写图书管理系统连接数据库，要求两个表，一个读者表（有用户名和密码两个数据），一个书籍表（有书名，ISBN，作者，出版社四个数据），要增删改查的代码

好的，下面是Java代码实现图书管理系统连接数据库，包括读者表和书籍表的增删改查操作。请确认你已经创建了名为“library”的数据库，并在其中创建了名为“reader”和“book”的两个表。

import java.sql.*;

public class LibraryManagementSystem {
    // 数据库连接信息
    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/library";
    private static final String USER = "root";
    private static final String PASSWORD = "password";

    private Connection conn = null;
    private Statement stmt = null;

    // 构造函数
    public LibraryManagementSystem() {
        try {
            // 注册 JDBC 驱动器
            Class.forName(JDBC_DRIVER);

            // 打开连接
            System.out.println("连接数据库...");
            conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);

            // 创建语句
            System.out.println("创建语句...");
            stmt = conn.createStatement();

        } catch (SQLException se) {
            // 处理 JDBC 错误
            se.printStackTrace();
        } catch (Exception e) {
            // 处理 Class.forName 错误
            e.printStackTrace();
        }
    }

    // 关闭连接
    public void close() {
        try {
            if (stmt != null) stmt.close();
        } catch (SQLException se2) {
        } // 什么都不做
        try {
            if (conn != null) conn.close();
        } catch (SQLException se) {
            se.printStackTrace();
        }
        System.out.println("已关闭数据库连接。");
    }

    // 读者表的增删改查
    public void addReader(String username, String password) {
        try {
            String sql = "INSERT INTO reader (username, password) VALUES ('" + username + "', '" + password + "')";
            stmt.executeUpdate(sql);
            System.out.println("已添加读者：" + username);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void deleteReader(String username) {
        try {
            String sql = "DELETE FROM reader WHERE username='" + username + "'";
            stmt.executeUpdate(sql);
            System.out.println("已删除读者：" + username);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void updateReader(String username, String newPassword) {
        try {
            String sql = "UPDATE reader SET password='" + newPassword + "' WHERE username='" + username + "'";
            stmt.executeUpdate(sql);
            System.out.println("已修改读者密码：" + username);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void queryReader(String username) {
        try {
            String sql = "SELECT * FROM reader WHERE username='" + username + "'";
            ResultSet rs = stmt.executeQuery(sql);
            if (rs.next()) {
                String password = rs.getString("password");
                System.out.println("读者信息：用户名：" + username + "，密码：" + password);
            } else {
                System.out.println("读者不存在：" + username);
            }
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    // 书籍表的增删改查
    public void addBook(String bookname, String ISBN, String author, String publisher) {
        try {
            String sql = "INSERT INTO book (bookname, ISBN, author, publisher) VALUES ('" + bookname + "', '" + ISBN + "', '" + author + "', '" + publisher + "')";
            stmt.executeUpdate(sql);
            System.out.println("已添加书籍：" + bookname);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void deleteBook(String bookname) {
        try {
            String sql = "DELETE FROM book WHERE bookname='" + bookname + "'";
            stmt.executeUpdate(sql);
            System.out.println("已删除书籍：" + bookname);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void updateBook(String bookname, String newPublisher) {
        try {
            String sql = "UPDATE book SET publisher='" + newPublisher + "' WHERE bookname='" + bookname + "'";
            stmt.executeUpdate(sql);
            System.out.println("已修改书籍出版社：" + bookname);
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    public void queryBook(String bookname) {
        try {
            String sql = "SELECT * FROM book WHERE bookname='" + bookname + "'";
            ResultSet rs = stmt.executeQuery(sql);
            if (rs.next()) {
                String ISBN = rs.getString("ISBN");
                String author = rs.getString("author");
                String publisher = rs.getString("publisher");
                System.out.println("书籍信息：书名：" + bookname + "，ISBN：" + ISBN + "，作者：" + author + "，出版社：" + publisher);
            } else {
                System.out.println("书籍不存在：" + bookname);
            }
        } catch (SQLException se) {
            se.printStackTrace();
        }
    }

    // 测试
    public static void main(String[] args) {
        LibraryManagementSystem lms = new LibraryManagementSystem();
        lms.addReader("Alice", "123456");
        lms.addReader("Bob", "654321");
        lms.addBook("Java编程思想", "978-7-121-34023-2", "Bruce Eckel", "机械工业出版社");
        lms.addBook("Thinking in Java", "978-7-115-20551-1", "Bruce Eckel", "机械工业出版社");
        lms.queryReader("Alice");
        lms.queryReader("Charlie");
        lms.updateReader("Bob", "abcdef");
        lms.deleteReader("Charlie");
        lms.queryBook("Java编程思想");
        lms.queryBook("Python机器学习");
        lms.updateBook("Thinking in Java", "人民邮电出版社");
        lms.deleteBook("Python机器学习");
        lms.close();
    }
}

注意：上述代码中的数据库连接信息、表名、字段名等需要根据实际情况进行修改。为了防止 SQL 注入攻击，这里没有使用 PreparedStatement，实际使用中建议使用 PreparedStatement。