ERORR:
[17:45:39] [Server thread/ERROR]: Error occurred while enabling BookOnlinePlayers v1.0 (Is it up to date?)
java.lang.NullPointerException
	at me.drbooker.bookplayersonline.mysql.MySQL.update(MySQL.java:49) ~[?:?]
	at me.drbooker.bookplayersonline.Main.ConnectMySQL(Main.java:46) ~[?:?]
	at me.drbooker.bookplayersonline.Main.onEnable(Main.java:19) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:271) ~[spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.craftbukkit.v1_11_R1.CraftServer.enablePlugin(CraftServer.java:376) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.craftbukkit.v1_11_R1.CraftServer.enablePlugins(CraftServer.java:326) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.craftbukkit.v1_11_R1.CraftServer.reload(CraftServer.java:750) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.Bukkit.reload(Bukkit.java:540) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:25) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at org.bukkit.craftbukkit.v1_11_R1.CraftServer.dispatchCommand(CraftServer.java:650) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.PlayerConnection.handleCommand(PlayerConnection.java:1354) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.PlayerConnection.a(PlayerConnection.java:1189) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_131]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_131]
	at net.minecraft.server.v1_11_R1.SystemUtils.a(SourceFile:46) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.MinecraftServer.D(MinecraftServer.java:747) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.DedicatedServer.D(DedicatedServer.java:399) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.MinecraftServer.C(MinecraftServer.java:678) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at net.minecraft.server.v1_11_R1.MinecraftServer.run(MinecraftServer.java:576) [spigot.jar:git-Spigot-3fb9445-fbb47e8]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]

Main:
package me.drbooker.bookplayersonline;

import org.bukkit.Bukkit;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.java.JavaPlugin;

import me.drbooker.bookplayersonline.mysql.MySQL;
import me.drbooker.bookplayersonline.mysql.SQLPlayers;

public class Main extends JavaPlugin {

	public static Plugin pl;
	public static MySQL mysql;

	@Override
	public void onEnable() {
		pl = this;

		ConnectMySQL();

		saveDefaultConfig();
		Bukkit.getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
			@Override
			public void run() {
				SQLPlayers.setPlayers(Main.getInst().getConfig().getString("server"), Bukkit.getOnlinePlayers().size());
			}
		}, 0, 1200L);
	}

	@Override
	public void onDisable() {
		pl = null;
	}

	public static Plugin getInst() {
		return pl;
	}

	private void ConnectMySQL() {
		mysql = new MySQL("localhost", "baza", "nick", "haslo");
		mysql.update("CREATE TABLE IF NOT EXISTS BookSerwery (ID INT NOT NULL AUTO_INCREMENT, SERWER VARCHAR(16), PLAYERS INT NOT NULL, PRIMARY KEY (ID), UNIQUE (SERWER));");
	}
}

MySQL:
package me.drbooker.bookplayersonline.mysql;

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

public class MySQL {

	private String HOST = "localhost";
	private String DATABASE = "baza";
	private String USER = "user";
	private String PASSWORD = "password";

	private Connection con;

	public MySQL(String host, String database, String user, String password) {
		this.HOST = host;
		this.DATABASE = database;
		this.USER = user;
		this.PASSWORD = password;

		connect();
	}

	public void connect() {
		try {
			con = DriverManager.getConnection("jdbc:mysql://" + HOST + ":3306/" + DATABASE + "?autoReconnect=true", USER, PASSWORD);
			System.out.println("[MySQL] Polaczono z baza MySQL.");
		} catch (SQLException e) {
			System.out.println("[MySQL] Polaczenie z baza MySQL nie powiodlo sie! Blad: " + e.getMessage());
		}
	}

	public void close() {
		try {
			if(con != null) {
				con.close();
				System.out.println("[MySQL] Rozlaczenie z baza MySQL zakonczylo sie pomyslnie!");
			}
		} catch (SQLException e) {
			System.out.println("[MySQL] Rozlaczanie z baza MySQL nie powiodlo sie! Blad: " + e.getMessage());
		}
	}

	public void update(String qry) {
		try {
			Statement st = con.createStatement();
			st.executeUpdate(qry);
			st.close();
		} catch (SQLException e) {
			connect();
			System.err.println(e);
		}
	}

	public ResultSet query(String qry) {
		ResultSet rs = null;

		try {
			Statement st = con.createStatement();
			rs = st.executeQuery(qry);
		} catch (SQLException e) {
			connect();
			System.err.println(e);
		}
		return rs;
	}
}