如何在读取数据库时捕获重复值并显示消息框？

import java.sql.*;

public class DatabaseReader {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";
        int duplicateCount = 0;

        try {
            Connection connection = DriverManager.getConnection(url, username, password);
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery("SELECT * FROM mytable");

            while (resultSet.next()) {
                String value = resultSet.getString("column_name");

                // Check if the value already exists in previous records
                if (checkDuplicate(value)) {
                    duplicateCount++;
                    System.out.println("Duplicate value found: " + value);
                }
            }

            resultSet.close();
            statement.close();
            connection.close();

            if (duplicateCount > 0) {
                // Display a message box with the duplicate count and handling instructions
                showMessage("Duplicate values found", "Total duplicates: " + duplicateCount + "\nPlease handle accordingly.");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static boolean checkDuplicate(String value) {
        // Implement your logic to check if the value already exists in previous records
        // Return true if duplicate, false otherwise
        // You can use data structures like Set or Map to store previous values for efficient duplicate checking
        return false;
    }

    private static void showMessage(String title, String message) {
        // Implement your logic to display a message box with the given title and message
        // This can be done using a GUI framework or library
        // Provide handling instructions to the user
    }
}