java数据库代码

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java，import java.sql.Connection;，import java.sql.DriverManager;，import java.sql.ResultSet;，import java.sql.Statement;，，public class DatabaseExample {，    public static void main(String[] args) {，        try {，            // 加载数据库驱动，            Class.forName("com.mysql.jdbc.Driver");，，            // 连接数据库，            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test_db", "username", "password");，，            // 创建Statement对象，            Statement statement = connection.createStatement();，，            // 执行SQL查询，            ResultSet resultSet = statement.executeQuery("SELECT * FROM users");，，            // 处理查询结果，            while (resultSet.next()) {，                int id = resultSet.getInt("id");，                String name = resultSet.getString("name");，                System.out.println("ID: " + id + ", Name: " + name);，            }，，            // 关闭资源，            resultSet.close();，            statement.close();，            connection.close();，        } catch (Exception e) {，            e.printStackTrace();，        }，    }，}，

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以下是一个简单的Java数据库代码示例，使用了JDBC（Java Database Connectivity）来连接和操作MySQL数据库，在这个示例中，我们将创建一个名为"students"的表，并插入一些数据。

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
public class DatabaseExample {
    public static void main(String[] args) {
        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/test_db";
        String user = "root";
        String password = "your_password";
        // 加载驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return;
        }
        // 连接数据库
        try (Connection connection = DriverManager.getConnection(url, user, password)) {
            // 创建表
            String createTableSQL = "CREATE TABLE IF NOT EXISTS students (" +
                    "id INT PRIMARY KEY AUTO_INCREMENT," +
                    "name VARCHAR(50) NOT NULL," +
                    "age INT NOT NULL," +
                    "grade VARCHAR(10) NOT NULL" +
                    ")";
            try (PreparedStatement preparedStatement = connection.prepareStatement(createTableSQL)) {
                preparedStatement.executeUpdate();
                System.out.println("Table 'students' created successfully!");
            }
            // 插入数据
            String insertDataSQL = "INSERT INTO students (name, age, grade) VALUES (?, ?, ?)";
            try (PreparedStatement preparedStatement = connection.prepareStatement(insertDataSQL)) {
                preparedStatement.setString(1, "张三");
                preparedStatement.setInt(2, 18);
                preparedStatement.setString(3, "高三");
                int rowsAffected = preparedStatement.executeUpdate();
                System.out.println("Inserted " + rowsAffected + " row(s) into 'students' table.");
            }
            // 查询数据
            String queryDataSQL = "SELECT * FROM students";
            try (PreparedStatement preparedStatement = connection.prepareStatement(queryDataSQL)) {
                java.sql.ResultSet resultSet = preparedStatement.executeQuery();
                while (resultSet.next()) {
                    int id = resultSet.getInt("id");
                    String name = resultSet.getString("name");
                    int age = resultSet.getInt("age");
                    String grade = resultSet.getString("grade");
                    System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age + ", Grade: " + grade);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

在这个示例中，我们首先加载了MySQL的JDBC驱动，然后使用DriverManager.getConnection()方法连接到数据库，接下来，我们创建了一个名为"students"的表，并插入了一些数据，我们查询了表中的所有数据并将其打印到控制台。