Main Class

package com.jartexnetwork.skyblock.gui;

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

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.Listener;
import org.bukkit.event.inventory.InventoryClickEvent;
import org.bukkit.inventory.Inventory;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;
import org.bukkit.inventory.meta.SkullMeta;
import org.bukkit.plugin.java.JavaPlugin;

public class Main extends JavaPlugin implements Listener{

    static Connection connection;
    static Statement statement;
    public void onEnable() {
        this.getConfig().options().copyDefaults();
        saveConfig();
        Bukkit.getServer().getPluginManager().registerEvents(this, this);

        try { //We use a try catch to avoid errors, hopefully we don't get any.
            Class.forName("com.mysql.jdbc.Driver"); //this accesses Driver in jdbc.
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            System.err.println("jdbc driver unavailable!");
            return;
        }
        /*final String url = this.getConfig().getString("Url");
        final String username = this.getConfig().getString("Username");
        final String password = this.getConfig().getString("Password");*/
        try { //Another try catch to get any SQL errors (for example connections errors)
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/spawnerrankupsystem","root","JartexRene98");
            //with the method getConnection() from DriverManager, we're trying to set
            //the connection's url, username, password to the variables we made earlier and
            //trying to get a connection at the same time. JDBC allows us to do this.
        } catch (SQLException e) { //catching errors)
            e.printStackTrace(); //prints out SQLException errors to the console (if any)
            System.err.println("Failed connection with MySQL");
            Bukkit.getPluginManager().disablePlugin(this);
        }
    }


    public void onDisable() {
        try { //using a try catch to catch connection errors (like wrong sql password...)
            if(connection!=null && !connection.isClosed()){ //checking if connection isn't null to
                //avoid recieving a nullpointer
                connection.close(); //closing the connection field variable.
            }
        }catch(Exception e){
            e.printStackTrace();

        }
        Bukkit.getServer().getLogger().info("SpawnerRankupSystem is Disabled!");
    }


    public void OnCommand(CommandSender sender, Command cmd, String label, String[] args) {
        String p = sender.getName().toLowerCase();

        int stage = 0;
        int heads = 0;
        boolean money = false;
        if(cmd.getName().equalsIgnoreCase("Spawner")) {


            try {
                statement = connection.createStatement();
            } catch (SQLException ignored) {}

            String sql = "SELECT spawnerrankupsystem "
                    + "FROM players"
                    + "WHERE  name LIKE '%' + name + '%' ";
            String sql2 = "INSERT into players"
                    + "playername, stage, heads, money"
                    + "VALUES(" + p + ", " + stage + ", " + heads + ", " + money;

            try {
                statement.executeQuery(sql);
            } catch (SQLException ignored) {
                try {
                    statement.executeQuery(sql2);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }


            ItemStack skull = new ItemStack(Material.SKULL_ITEM, 1, (short) 3);
            ItemStack skull2 = (ItemStack)skull.getItemMeta();
            ((SkullMeta) skull2).setOwner("MHF_ArrowUp");
            ((ItemMeta) skull2).setDisplayName(ChatColor.GOLD + "RANKUP");
            Inventory inv = Bukkit.createInventory(null, 8, ChatColor.DARK_AQUA + "Spawner GUI");
            inv.setItem(0, skull2);
            inv.setItem(4, new ItemStack(Material.MOB_SPAWNER));


            ArrayList<String> lore = new ArrayList<String>();
            //Formula heads needed: 500+55x^2
            double percentage = 6;
            int amount = (int) Math.floor(percentage);
            lore.add("Status:" + amount);
            ItemStack ladder = new ItemStack(Material.LADDER, 1 , (short) 0);
            ItemMeta Ladder = ladder.getItemMeta();
            inv.setItem(8, new ItemStack(Material.LADDER));
            Player player = Bukkit.getPlayer(p);
            Ladder.setLore(lore);
            ladder.setItemMeta((ItemMeta) ladder);
            player.openInventory(inv);
        }
    }


    public void onInventoryClickEvent(InventoryClickEvent e) {
        if(e.getInventory().getName().equalsIgnoreCase("Spawner"))
            return;
        Player p = (Player) e.getWhoClicked();
        e.setCancelled(true);

        if(e.getCurrentItem()==null || e.getCurrentItem().getType()==Material.AIR||!e.getCurrentItem().hasItemMeta()){
            p.closeInventory();
            return;
        }

        switch(e.getCurrentItem().getType()) {
        case SKULL_ITEM:
            Inventory rankUp = Bukkit.createInventory(null, 53, ChatColor.BLUE + "RANKUP");
            ItemStack dye = new ItemStack(Material.INK_SACK, 1, (short) 10);
            rankUp.setItem(47, new ItemStack(dye));
            rankUp.setItem(51, new ItemStack(Material.GOLD_BLOCK));
            p.closeInventory();
            p.openInventory(rankUp);
            break;
        case MOB_SPAWNER:
            Inventory spawners = Bukkit.createInventory(null, 17, ChatColor.DARK_GREEN + "Spawners");
            String[] Aspawners = {"Pig","Cow","Sheep","Chicken","Mooshroom",
                    "Skeleton","Zombie","Creeper","Spider","Blaze","Enderman",
                    "Slime","Pigman","Cavespider","Iron Golem"};
            for(int i=0; i <= Aspawners.length; i++) {
                if(p.hasPermission("silkspawners.place." + Aspawners[i])){
                    ItemStack spawner = new ItemStack(Material.MOB_SPAWNER);
                    spawner.getItemMeta().setDisplayName(ChatColor.YELLOW + Aspawners[i] + "Spawner");
                    spawners.setItem(i, spawner);
                }
            }
            p.closeInventory();
            p.openInventory(spawners);
            break;
        case LADDER:
            p.closeInventory();
            break;
        default:
            p.closeInventory();
            break;

        }
    }

}