config.yml

##DEconomy 1.0 made for Dungeons owned by Harry created by TheMasteredPanda.

DEconomy:
  #If you don't know what this is. then it would be wise not to touch it.
  ThreadPoolSize: 40
  #Allow normal players to view other players bank balances.
  BalanceViewing: false
  #Prefix for all the plugin to player messages.
  Prefix: '&aDEconomy &8»&7'
  #Line header and footer used for all box messages.
  Line: '&7&m-------------------------------'
  #Information line.
  PageInfoLine: '&8(&7{currentpage}&8/&7{maxpages}&8) &7{command} {nextpage}'
  #Default lore and name for the page directors in the villager shops.
  GUI:
    PageDirector:
      Lore:
        - '&7» &7Click to go to next page. :)'
      Name: '&7» &aClick to go to the next page.'
  #Limit - Amount of banks any user can own at one time.
  #Enabled - If the bank feature is enabled on this server.
  Banks:
    #If the feature is enabled.
    Enabled: true
    #Default amount of banks any user without op or admin perms can own. If a player has deconomy.banks.<number of bank> it will override the default limit.
    Limit: 5
    #For /deconomy banks
    BankEntryTemplate: '&aBank: &7{bank} &8- &aAccessibility: &7{accesstype}'
  SQL:
    UsingSQLite: true
    #If UsingSQLite is true, don't bother with filling this out.
    MySQL:
      Address:
      Port:
      Database:
      Username:
      Password:
      MaximumPoolSize: 10
  Shop:
    #This value corresponds to the multiplier in the shop. When a person shift + left/right click
    Multipler: 8
#All messages
Messages:
  NoPermission:
    Shop: '{prefix} &cYou do not have permission to use shop {shopname}.'
    Sign: '{prefix} &cYou do not have permission to use the sign.'
  OpeningShop: '{prefix} &aOpening shop {shopname}.'
  CannotBuyItem: '{prefix} &cYou cannot buy item {item}.'
  NotEnoughMoney:
    Shop: '{prefix} &cYou do not have enough money to {tradetype} {item} for {price}.'
    Bank: '{prefix} &c{bank} does not have enough money for a withdrawal of {amount}.'
    Player: '{prefix} &cYou do not have enough money to {action}.'
  SuccessfullyBrought: '{prefix} &aYou successfully brought {item} for {price}.'
  CannotSellItem: '{prefix} &cYou cannot sell item {item}.'
  SuccessfullySold: '{prefix} &cYou successfully sold item {item} for {price}.'
  ClosingShop: '{prefix} &Closing shop {shopname}.'
  CannotViewOtherBalances: '{prefix} &cYou do not have permission to view other peoples balances.'
  PlayerNotFound: '{prefix} &cCould not find player {player}.'
  PlayerBalanceInfo: '{prefix} {player}s balance is: {balance}.'
  DEconomyHelpList:
  - '{line}'
  - '&a /deconomy bal | /deconomy bal <player name>'
  - '&a /deconomy bank'
  - '{line}'
  BankHelpList:
  - '{line}'
  - '&a /deconomy bank create <bank name>'
  - '&a /deconomy bank deposit <bank name> <amount>'
  - '&a /deconomy bank withdraw <bank name> <amount>'
  - '&a /deconomy bank leave <bank name>'
  - '&a /deconomy bank delete <bank name>'
  - '&a /deconomy bank info <bank name>'
  - '{line}'
  NotEnoughArguments: '{prefix} &cNot enough arguments given to successfully execute command {commandusage}.'
  BankNotFound: '{prefix} &cCould not find bank {bank}.'
  ArgumentsNotANumber: 'Arguments specified does not include a number. {commandusage}.'
  SuccessfullyDeposited: '{prefix} &aSuccessfully deposited {amount} into {bank}.'
  NotEnoughMoney: '{prefix} &cYou do not have enough money to do this.'
  SuccessfullyWithdrew: '{prefix} &aSuccessfully withdrew {amount} from {bank}.'
  NotTheBankOwner: '{prefix} &cYou do not own this bank so you cannot do this.'
  RemovedFromBank: '{prefix} &aYou are no longer a member of {bank}.'
  Sudo:
    Successfully:
      RemovedItems: '{prefix} &aSuccessfully removed item {item} from shop {shop}.'
      Changed:
        BothPrices: '{prefix} &aSuccessfully changed both buy and sell prices for {item}.'
        BuyPrice: '{prefix} &aSuccessfully changed buy price for {item}.'
        SellPrice: '{prefix} &aSuccessfully changed sell price for {item}.'
    Disable: '{prefix} &cSudo disabled for {name}.'
    Enable: '{prefix} &aSudo Enabled for {name}.'
  AdminHelpList:
    - '{line}'
    - '&a /adeconomy create <permission> <name> <profession> &8- &7Create a villager shop.'
    - '&a /adeconomy remove <shopid> &8- &7Remove a shop.'
    - '&a /adeconomy bank info <bank name> &8- &7Get a players bank information.'
    - '&a /adeconomy bank remove <bank name> &8- &7Forcibly remove a bank.'
    - '&a /adeconomy withdraw <bank name> <amount> &8- &7Withdraw money from any bank.'
    - '&a /adeconomy bank deposit <bank name> <amount> &8- &7Deposit money into any bank.'
    - '&a /adeconomy bank transfer <bank name> <new owner> <remove old owner to member (yes|no) &8- &7Change the ownership of a bank.'
    - '&a /adeconomy member add <bank name> <player name> &8- &7Add a member to any bank.'
    - '&a /adeconomy member remove <bank name> <player name> &8- &7Remove a member of any bank.'
    - '{line}'
  ItemNotFound: '{prefix} &cItem advertised in the sign is not found.'
  SuccessfullyCreatedShop: '{prefix} &aSuccessfully created shop {shopName}.'
  SuccessfullyRemovedShop: '{prefix} &aSuccessfully removed shop {shopName}.'
  CantFindShop: '{prefix} &cCannot find shop {shopName}.'
  BankInfoList:
  - '{line}'
  - '&aOwner: &7{owner}'
  - '&aMembers: &7{members}'
  - '&aBank Balance: &7{balance}'
  - '{line}'
  SuccessfullyCreatedBank: '{prefix} Successfully created bank {bank}.'
  UnsuccessfullyCreatedShop: '{prefix} &cFailed to create bank. Seek further assistance from a Developer if need be.'
  TransferredOwnership: '{prefix} &aBank {bank}s ownership has been transferred to {bankowner}.'
  PlayerAlreadyABankMember: '{prefix} &cPlayer {player} is already a member of {bank}.'
  PlayerIsNotABankMember: '{prefix} &cPlayer {player} is not a member of {bank}.'
  RemovedBankMember: '{prefix} Player {player} has been removed from bank membership {bank}.'
  NoAccess: '{prefix} &cYou do not have access to bank {bank}.'
  NotAMember: '{prefix} &cYou are not a member of bank {bank}.'
  CannotLeaveBank: '{prefix} You cannot leave this bank, you are the owner of it! If you want to remove it either transfer the ownership over to another player or remove it altogether.'
  ContainsBannedWord: '{prefix} {name} contains a banned word, please choose another name that does not contain a banned word.'
  NoAccessibleBanksFound: '{prefix} &cWe could not find any banks that you had access to.'
  PageDoesNotExist: '{prefix} &cPage {pagenumber} does not exist.'
  AlreadyOwnsBankNamed: '{prefix} &cYou already own a bank named {bank}.'
  MaximumBanksMet: '{prefix} &cYou have hit or exceeded the limit of banks you are allowed to own.'
  BankDeleted: '{prefix} {bank} successfully deleted.'
  OwnershipTransferred: '{prefix} Ownership of {bank} has now been transferred to {newowner} from {oldowner}.'
  LeftBank: '{prefix} Left bank {bank}.'
  ContainsBannedWord: '{prefix} {name} contains a banned word, please choose another name that does not contain a banned word.'
  CannotPlaceTwoShopsInOneBlock: '{prefix} &cYou cannot place two shops in one block!'
  NameAlreadyUsed: '{prefix} &cThat name has already been used for a shop.'

MainConfig.java

ackage net.dungeons.config;

import com.google.common.collect.Lists;
import net.dungeons.DEconomy;
import net.dungeons.utils.Pair;
import org.bukkit.ChatColor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

import java.util.List;

/**
 * Created by TheMasteredPanda on 23/02/2017.
 */

public class MainConfig extends BaseConfig
{
    private DEconomy instance = DEconomy.getInstance();

    public MainConfig()
    {
        super("config.yml");
    }

    public void sendMessage(CommandSender sender, String messageNode, boolean color)
    {
        String message = this.config.getString(messageNode).replace("{prefix}", this.getPrefix().replace("{line}", this.getDEconomyContainerLine()));

        if (color) {
            sender.sendMessage(ChatColor.translateAlternateColorCodes('&', message));
        } else {
            sender.sendMessage(message);
        }
    }

    public void sendMessage(CommandSender sender, String messageNode, boolean color, Pair... pairs)
    {
        String message = this.config.getString(messageNode).replace("{prefix}", this.getPrefix().replace("{line}", this.getDEconomyContainerLine()));

        for (int i = 0; i < pairs.length; i++) {
            Pair pair = pairs[i];

            message = message.replace((String) pair.getLeft(), (String) pair.getRight());
        }

        if (color) {
            sender.sendMessage(ChatColor.translateAlternateColorCodes('&', message));
        } else {
            sender.sendMessage(this.config.getString(message));
        }
    }

    public void sendMessage(Player player, String messageNode, boolean color)
    {
        String message = this.config.getString(messageNode).replace("{prefix}", this.getPrefix().replace("{line}", this.getDEconomyContainerLine()));

        if (color) {
            player.sendMessage(ChatColor.translateAlternateColorCodes('&', message));
        } else {
            player.sendMessage(message);
        }
    }

    public void sendMessage(Player player, String messageNode, boolean color, Pair... pairs)
    {
        String message = this.config.getString(messageNode).replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine());

        for (int i = 0; i < pairs.length; i++) {
            Pair pair = pairs[i];
            message = message.replace((String) pair.getLeft(), (String) pair.getRight());
        }

        if (color) {
            player.sendMessage(ChatColor.translateAlternateColorCodes('&', message));
        } else {
            player.sendMessage(this.config.getString(message));
        }
    }

    public void sendMessages(CommandSender sender, String messageNode, boolean color)
    {
        if (color) {
            this.config.getStringList(messageNode).forEach(line -> sender.sendMessage(ChatColor.translateAlternateColorCodes('&', line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine()))));
        } else {
            this.config.getStringList(messageNode).forEach(line -> sender.sendMessage(line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine())));
        }
    }

    public void sendMessages(CommandSender sender, String messageNode, boolean color, Pair... pairs)
    {
        List<String> content = Lists.newArrayList();

        this.config.getStringList(messageNode).forEach(line -> {
            String message = line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine());

            for (Pair pair : pairs) {
                message = message.replace((String) pair.getLeft(), (String) pair.getRight());
            }

            if (color) {
                message = ChatColor.translateAlternateColorCodes('&', message);
            }
            content.add(message);
        });

        content.forEach(sender::sendMessage);
    }

    public void sendMessages(Player player, String messageNode, boolean color)
    {
        if (color) {
            this.config.getStringList(messageNode).forEach(line -> player.sendMessage(ChatColor.translateAlternateColorCodes('&', line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine()))));
        } else {
            this.config.getStringList(messageNode).forEach(line -> player.sendMessage(line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine())));
        }
    }

    public void sendMessages(Player player, String messageNode, boolean color, Pair... pairs)
    {
        System.out.println(messageNode + "\n" + pairs);

        List<String> content = Lists.newArrayList();

        this.config.getStringList(messageNode).forEach((String line) -> {
            String message = line.replace("{prefix}", this.getPrefix()).replace("{line}", this.getDEconomyContainerLine());

            for (Pair pair : pairs) {
                message = message.replace((String) pair.getLeft(), (String) pair.getRight());
            }

            if (color) {
                message = ChatColor.translateAlternateColorCodes('&', message);
            }
            content.add(message);
        });

        System.out.println(content);

        content.forEach(player::sendMessage);
    }

    public List<String> getDefaultPageDirectorLore()
    {
        return this.config.getStringList("DEconomy.GUI.PageDirector.Lore");
    }

    public String getDefaultPageDirectorName()
    {
        return this.config.getString("DEconomy.GUI.PageDirector.Name");
    }

    public List<String> getShopEntryLore()
    {
        List<String> lore = this.config.getStringList("Shop.Entry.Lore");
        lore.forEach(line -> line = ChatColor.translateAlternateColorCodes('&', line));

        return lore;
    }

    public String getPrefix()
    {
        return ChatColor.translateAlternateColorCodes('&', this.config.getString("DEconomy.Prefix"));
    }

    public boolean getBankSupport()
    {
        return this.config.getBoolean("DEconomy.Banks.Enabled");
    }

    public boolean getUsingSQLite()
    {
        return this.config.getBoolean("DEconomy.SQL.UsingSQLite");
    }

    public String getMySQLAddress()
    {
        return this.config.getString("DEconomy.SQL.MySQL.Address");
    }

    public int getMySQLPort()
    {
        return this.config.getInt("DEconomy.SQL.MySQL.Port");
    }

    public String getMySQLDatabase()
    {
        return this.config.getString("DEconomy.SQL.MySQL.Database");
    }

    public String getMySQLUsername()
    {
        return this.config.getString("DEconomy.SQL.MySQL.Username");
    }

    public String getMySQLPassword()
    {
        return this.config.getString("DEconomy.SQL.MySQL.Password");
    }

    public int getMySQLPoolSize()
    {
        return this.config.getInt("DEconomy.SQL.MySQL.MaximumPoolSize");
    }

    public int getDEconomyThreadPool()
    {
        return this.config.getInt("DEconomy.ThreadPoolSize");
    }

    public boolean getViewingOtherBalances()
    {
        return this.config.getBoolean("DEconomy.BalanceViewing");
    }

    public String getBankEntryTemplate()
    {
        return this.config.getString("DEconomy.Banks.BankEntryTemplate");
    }

    public String getDEconomyContainerLine()
    {
        return this.config.getString("DEconomy.Line");
    }

    public String getDEconomyContainerInfoPage()
    {
        return this.config.getString("DEconomy.PageInfoLine");
    }

    public int getMaximumAllowedBanksOwned()
    {
        return this.config.getInt("DEconomy.Banks.Limit");
    }

    public int getShopMultiplier()
    {
        return this.config.getInt("DEconomy.Shop.Multiplier");
    }
}

Shop.java

package net.dungeons.shop.villager;

import lombok.Getter;
import net.dungeons.DEconomy;
import net.dungeons.config.MainConfig;
import net.dungeons.config.ShopTemplateConfig;
import net.dungeons.shop.villager.page.DEconomyGUI;
import net.dungeons.shop.villager.page.GUIListeners;
import net.dungeons.shop.villager.page.GUIPage;
import net.dungeons.utils.InventoryUtils;
import net.dungeons.utils.Pair;
import net.dungeons.utils.ShopUtils;
import net.milkbowl.vault.economy.Economy;
import org.bukkit.entity.Entity;
import org.bukkit.entity.Player;
import org.bukkit.entity.Villager;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.EntityDamageByEntityEvent;
import org.bukkit.event.inventory.InventoryClickEvent;
import org.bukkit.event.inventory.InventoryCloseEvent;
import org.bukkit.event.inventory.InventoryOpenEvent;
import org.bukkit.event.inventory.InventoryType;
import org.bukkit.event.player.PlayerInteractEntityEvent;
import org.bukkit.inventory.ItemStack;

import java.util.stream.Stream;

/**
 * Created by TheMasteredPanda on 02/02/2017.
 */

public class Shop implements GUIListeners, Listener
{
    private @Getter String shopName;
    private @Getter String permission;
    private @Getter DEconomyGUI gui;
    private @Getter String id;
    private @Getter Villager shopKeeper;
    private MainConfig config;
    private DEconomy instance;
    private Economy economy;
    private @Getter ShopTemplateConfig shopConfig;

    public Shop(DEconomy instance, ShopKeeperMeta shopKeeperMeta, DEconomyGUI gui, ShopTemplateConfig shopConfig, boolean newShop)
    {
        this(instance, shopKeeperMeta, gui, newShop);
        this.shopConfig = shopConfig;
    }

    public Shop(DEconomy instance, ShopKeeperMeta shopKeeperMeta, DEconomyGUI gui, boolean newShop)
    {
        this.instance = instance;
        this.economy = instance.getEconomy();
        this.gui = gui;
        this.gui.addGUIListeners(this);

        instance.debug("ShopKeeperMeta: " + shopKeeperMeta + ", DEconomy: " + gui + ", newShop: " + newShop);
        instance.debug(shopKeeperMeta.toString());

        this.shopName = shopKeeperMeta.getName();
        this.permission = shopKeeperMeta.getPermission();

        if (newShop) {
            instance.debug("Shop is a new shop.");

            if (this.shopKeeper == null) {
                this.shopKeeper = ShopUtils.spawnVillager(shopKeeperMeta);
                this.shopConfig = new ShopTemplateConfig(shopKeeperMeta);
            }

            this.reload();
            return;
        } else {
            instance.debug("Shop is not a new shop.");
            Entity[] entities = shopKeeperMeta.getLocation().getChunk().getEntities();

            System.out.println("Shop Keeper UUID is: " + shopKeeperMeta.getVillagerUniqueID());
            Stream.of(entities).forEach(entity -> {
                instance.debug("Currently iterating though entity: " + entity.getName() + " with uuid " + entity.getUniqueId());

                if (entity.getUniqueId().equals(shopKeeperMeta.getVillagerUniqueID())) {
                    instance.debug("Entity " + entity.getName() + " has the same unique id as " + shopKeeperMeta.getVillagerUniqueID());
                    this.shopKeeper = (Villager) entity;
                }
            });

            if (this.shopKeeper == null) {
                this.shopKeeper = ShopUtils.spawnVillager(shopKeeperMeta);
            }
        }

        this.id = shopKeeperMeta.getId();
        this.config = instance.getConfigManager().getMainConfig();
        instance.getServer().getPluginManager().registerEvents(this, instance);
    }

    public void reload()
    {
        this.shopConfig.loadShop();
        this.instance.getShopManager().getShops().remove(this);
    }

    @EventHandler
    public void onInteract(PlayerInteractEntityEvent e)
    {
        if (!(e.getRightClicked() instanceof Villager)) {
            return;
        }

        Villager villager = (Villager) e.getRightClicked();

        if (!villager.getUniqueId().equals(this.shopKeeper.getUniqueId())) {
            return;
        }

        e.setCancelled(true);

        Player p = e.getPlayer();

        if (!p.hasPermission(this.permission)) {
            this.config.sendMessage(p, "Messages.NoPermission.Shop", true, new Pair("{shop}", this.shopName));
            return;
        }

        if (this.gui.getFirstPage() == null) {
            this.config.sendMessage(p, "Messages.NoPagesInShop", true, new Pair("{shop}", this.shopName));
            return;
        }

        p.openInventory(this.gui.getFirstPage().getInventory());
    }

    @EventHandler
    public void onDamage(EntityDamageByEntityEvent e)
    {
        if (!(e.getEntity() instanceof Villager)) {
            return;
        }

        Villager villager = (Villager) e.getEntity();

        if (!villager.getUniqueId().equals(this.shopKeeper.getUniqueId())) {
            return;
        }

        e.setCancelled(true);
    }

    public void onOpen(InventoryOpenEvent e, GUIPage page)
    {
        if (e.getInventory().getType() == InventoryType.MERCHANT) {
            e.setCancelled(true);
        }
    }



    public void onClick(InventoryClickEvent e, GUIPage page, boolean isPageDirector, ShopEntry shopEntry)
    {
        Player p = (Player) e.getWhoClicked();
        double balance = this.instance.getEconomy().getBalance(p);

        if (shopEntry == null) {
            return;
        }

        String name = shopEntry.getItem().getItemMeta().getDisplayName();

        //Single - buy/sell one item per click
        if (e.getClick() == shopEntry.getType().getSingle() || shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL) {
            if (shopEntry.getType() == ShopEntry.Type.BUY || (shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL && e.getClick() == ShopEntry.Type.BUY.getSingle())) {
                double price = shopEntry.getBuyPrice();

                if (balance < price) {
                    this.config.sendMessage(p, "Messages.NotEnoughMoney.Shop", true); /*new Pair("{tradetype}", "buy"), new Pair("{item}", name), new Pair("{price}", price)*/
                    return;
                }

                if (this.economy.withdrawPlayer(p, shopEntry.getBuyPrice()).transactionSuccess()) {
                    this.config.sendMessage(p, "Messages.SuccessfullyBrought", true, new Pair("{item}", name));
                    InventoryUtils.addItems(p.getInventory(), new ItemStack[] {shopEntry.getItem()}, p.getLocation());
                }
            }

            if (shopEntry.getType() == ShopEntry.Type.SELL || (shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL && e.getClick() == ShopEntry.Type.SELL.getSingle())) {
                double price = shopEntry.getSellPrice();

                if (!p.getInventory().contains(shopEntry.getItem())) {
                    this.config.sendMessage(p, "Messages.ItemNotFound", true);
                    return;
                }

                boolean removedItem = false;

                for (ItemStack item : p.getInventory().getContents()) {
                    if (!item.getType().equals(shopEntry.getItem().getType())) {
                        continue;
                    }

                    if (item.getAmount() > 1) {
                        int amount =- item.getAmount();
                        item.setAmount(amount);
                        removedItem = true;
                        break;
                    } else {
                        p.getInventory().remove(item);
                        removedItem = true;
                    }
                }

                if (removedItem) {
                    if (this.economy.depositPlayer(p, price).transactionSuccess()) {
                        this.config.sendMessage(p, "Messages.SuccessfullySold", true, new Pair("{item}", name));
                        return;
                    }
                } else {
                    throw new IllegalArgumentException("Didn't remove item " + name + ".");
                }
            }
        }

        //Multiple - buy/sell a bulk amount that is set in the config
        if (e.getClick() == shopEntry.getType().getMultiple() || shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL) {
            String multiplierName = name + " x" + this.config.getShopMultiplier();

            if (shopEntry.getType() == ShopEntry.Type.BUY || (shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL && e.getClick() == ShopEntry.Type.BUY.getMultiple())) {
                double price = this.config.getShopMultiplier() * shopEntry.getBuyPrice();

                if (balance < price) {
                    this.config.sendMessage(p, "Messages.NotEnoughMoney.Shop", true, new Pair("{tradetype}", "buy"), new Pair("{item}", multiplierName), new Pair("{price}", this.economy.format(price)));
                    return;
                }

                if (this.economy.withdrawPlayer(p, price).transactionSuccess()) {
                    ItemStack itemStack = shopEntry.getItem().clone();
                    itemStack.setAmount(this.config.getShopMultiplier());

                    InventoryUtils.addItems(p.getInventory(), new ItemStack[] {itemStack}, p.getLocation());
                    this.config.sendMessage(p, "Messages.SuccessfullyBrought", true, new Pair("{item}", multiplierName));
                }
                return;
            }

            if (shopEntry.getType() == ShopEntry.Type.SELL || shopEntry.getType() == ShopEntry.Type.BUY_AND_SELL) {
                double price = this.config.getShopMultiplier() * shopEntry.getSellPrice();

                if (!p.getInventory().contains(shopEntry.getItem().getType())) {
                    this.config.sendMessage(p, "Message.ItemNotFound", true, new Pair("{item}", shopEntry.getItem().getType().name().toLowerCase()));
                    return;
                }

                boolean removedItems = false;

                int itemsToRemove = this.config.getShopMultiplier();

                for (ItemStack item : p.getInventory().getContents()) {
                    if (!item.getType().equals(shopEntry.getItem().getType())) {
                        continue;
                    }

                    if (item.getAmount() >= this.config.getShopMultiplier()) {
                        int amount = item.getAmount() - this.config.getShopMultiplier();
                        item.setAmount(amount);
                        removedItems = true;
                        break;
                    } else {
                        itemsToRemove = itemsToRemove - item.getAmount();
                        p.getInventory().remove(item);
                    }

                    if (itemsToRemove == 0) {
                        removedItems = true;
                        break;
                    }
                }

                if (removedItems) {
                    if (this.economy.depositPlayer(p, price).transactionSuccess()) {
                        this.config.sendMessage(p, "Messages.SuccessfullySold", true, new Pair("{item}", multiplierName));
                        return;
                    }
                } else {
                    throw new IllegalArgumentException("Didn't remove item " + multiplierName + ".");
                }
            }
        }
    }

    public void onClose(InventoryCloseEvent e, GUIPage page) {}

}

stacktrace

org.bukkit.event.EventException
        at org.bukkit.plugin.EventExecutor$1.execute(EventExecutor.java:46) ~[patched_1.11.2.jar:git-Paper-1081]
        at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:78) ~[patched_1.11.2.jar:git-Paper-1081]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[patched_1.11.2.jar:git-Paper-1081]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:517) ~[patched_1.11.2.jar:git-Paper-1081]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:502) ~[patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.PlayerConnection.a(PlayerConnection.java:1897) ~[patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.PacketPlayInWindowClick.a(SourceFile:33) ~[patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.PacketPlayInWindowClick.a(SourceFile:10) ~[patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:14) ~[patched_1.11.2.jar:git-Paper-1081]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_121]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_121]
        at net.minecraft.server.v1_11_R1.SystemUtils.a(SourceFile:46) [patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.MinecraftServer.D(MinecraftServer.java:830) [patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.DedicatedServer.D(DedicatedServer.java:403) [patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.MinecraftServer.C(MinecraftServer.java:754) [patched_1.11.2.jar:git-Paper-1081]
        at net.minecraft.server.v1_11_R1.MinecraftServer.run(MinecraftServer.java:652) [patched_1.11.2.jar:git-Paper-1081]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_121]
Caused by: java.lang.NullPointerException
        at net.dungeons.config.MainConfig.sendMessage(MainConfig.java:55) ~[?:?]
        at net.dungeons.shop.villager.Shop.onClick(Shop.java:176) ~[?:?]
        at net.dungeons.shop.villager.page.DEconomyGUI.onInventoryClick(DEconomyGUI.java:117) ~[?:?]
        at com.destroystokyo.paper.event.executor.asm.generated.GeneratedEventExecutor25.execute(Unknown Source) ~[?:?]
        at org.bukkit.plugin.EventExecutor$1.execute(EventExecutor.java:44) ~[patched_1.11.2.jar:git-Paper-1081]
        ... 16 more