如果数据库中存在数据，则返回的Java布尔函数

import java.sql.*;

public class DatabaseCheck {
    public static boolean checkDataExistence() {
        boolean dataExists = false;

        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";

        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

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

            // 创建查询语句
            String query = "SELECT COUNT(*) FROM table_name";

            // 执行查询
            statement = connection.createStatement();
            resultSet = statement.executeQuery(query);

            // 判断结果集中的数据是否大于0
            if (resultSet.next() && resultSet.getInt(1) > 0) {
                dataExists = true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭数据库连接
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        return dataExists;
    }
}

public class Main {
    public static void main(String[] args) {
        if (DatabaseCheck.checkDataExistence()) {
            System.out.println("数据存在！");
        } else {
            System.out.println("数据不存在！");
        }
    }
}