在Java中使用Boolean检查DB中是否存在值

import java.sql.*;

public class CheckValueInDB {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";
        String valueToCheck = "exampleValue";

        try {
            // 连接到数据库
            Connection connection = DriverManager.getConnection(url, username, password);

            // 创建查询语句
            String query = "SELECT * FROM mytable WHERE column_name = ?";

            // 创建PreparedStatement对象，并设置参数
            PreparedStatement statement = connection.prepareStatement(query);
            statement.setString(1, valueToCheck);

            // 执行查询
            ResultSet resultSet = statement.executeQuery();

            // 检查是否存在结果
            boolean exists = resultSet.next();

            // 输出结果
            if (exists) {
                System.out.println("值存在于数据库中");
            } else {
                System.out.println("值不存在于数据库中");
            }

            // 关闭连接
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}