understand this olllez

package io.github.thediamondpicks.bans;

import org.bukkit.Bukkit;
import org.bukkit.event.Listener;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * Created by TheDiamondPicks on 28/09/2016.
 */
public class Main extends JavaPlugin {
    private Connection connection;
    private String host, database, username, password;
    private int port;
    private static Plugin plugin;
    @Override
    public void onEnable() {
        getCommand("ban").setExecutor(new BanCommand());
        plugin = this;
        host = "jerryandjamy.com";
        port = 3306;
        database = "Bans";
        username = "nanana";
        password = "youthoughtwouldgetthepass";
        try {
            openConnection();
            Statement statement = connection.createStatement();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onDisable() {
        plugin = null; // Prevents mem leaks
    }
    //Much eaisier then registering events in 10 diffirent methods
    public static void registerEvents(org.bukkit.plugin.Plugin plugin, Listener... listeners) {
        for (Listener listener : listeners) {
            Bukkit.getServer().getPluginManager().registerEvents(listener, plugin);
        }
    }

    //To access the plugin variable from other classes
    public static Plugin getPlugin() {
        return plugin;
    }

    public void openConnection() throws SQLException, ClassNotFoundException {
        if (connection != null && !connection.isClosed()) {
            return;
        }

        synchronized (this) {
            if (connection != null && !connection.isClosed()) {
                return;
            }
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://" + this.host + ":" + this.port + "/" + this.database, this.username, this.password);
        }
    }
    BukkitRunnable r = new BukkitRunnable() {
        public void run() {
            try {
                openConnection();
                Statement statement = connection.createStatement();
            } catch(ClassNotFoundException e) {
                e.printStackTrace();
            } catch(SQLException e) {
                e.printStackTrace();
            }
        }
    };
}