ChestInterfaceItem.java

package com.empireminecraft.systems.chestui;

import com.empireminecraft.systems.EmpireChat;
import com.empireminecraft.util.BukkitUtil;
import com.empireminecraft.util.ItemUtil;
import com.google.common.base.Predicate;
import org.bukkit.entity.Player;
import org.bukkit.inventory.Inventory;
import org.bukkit.inventory.ItemStack;

import javax.annotation.Nullable;

public class ChestInterfaceItem extends ItemUtil.LoreBuilder {
    private Player player;
    private Inventory inventory;
    private int slot;
    private Predicate<Player> onClick = null;

    /**
     * Initiates a builder and sets the index to the first empty line after the lore
     *
     * @param item
     */
    public ChestInterfaceItem(Player player, Inventory inventory, int slot, ItemStack item) {
        super(item);
        this.player = player;
        this.inventory = inventory;
        this.slot = slot;
    }
    public ItemStack save() {
        ItemStack saved = super.save();
        inventory.setItem(slot, saved);
        return saved;
    }
    public ChestInterfaceItem onClick(Predicate<Player> run) {
        this.onClick = run;
        return this;
    }
    public ChestInterfaceItem onClick(final String cmd) {
        this.onClick = new Predicate<Player>() {
            @Override
            public boolean apply(@Nullable Player input) {
                EmpireChat.performCommand(player, cmd);
                return true;
            }
        };
        return this;
    }

    protected final void processClick() {
        if (onClick != null) {
            player.closeInventory();
            BukkitUtil.runTaskNextTick(new Runnable() {
                @Override
                public void run() {
                    onClick.apply(player);
                }
            });
        }
    }
}

ChestUI.java

package com.empireminecraft.systems.chestui;

import com.empireminecraft.util.BukkitUtil;
import com.empireminecraft.util.Util;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.inventory.InventoryAction;
import org.bukkit.event.inventory.InventoryClickEvent;
import org.bukkit.inventory.Inventory;

import java.util.HashMap;

public class ChestUI extends BukkitUtil.Listener {
    public static void initialize() {
        new ChestUI();
    }

    @EventHandler(ignoreCancelled = true)
    public void onInventoryClick(InventoryClickEvent event) {
        final Inventory inventory = event.getInventory();
        final HashMap<String, Object> meta = inventory.getMeta();
        if (!meta.containsKey("ChestUI")) {
            return;
        }
        event.setCancelled(true);

        if (event.getAction() != InventoryAction.PICKUP_ALL) {
            return;
        }
        if (event.getClickedInventory() != event.getView().getTopInventory()) {
            return;
        }
        final Object o = meta.get(ChestUIInterface.getSlotLabel(event.getSlot()));
        if (o instanceof ChestInterfaceItem) {
            ((ChestInterfaceItem) o).processClick();
        }
    }
    public static void open(Player player, Class <? extends ChestUIInterface> ui) {
        try {
            open(player, ui.newInstance());
        } catch (Exception e) {
            Util.printException(e);
        }
    }
    public static void open(Player player, ChestUIInterface ui) {
        try {
            final Inventory inventory = ui.initialize(player);
            inventory.getMeta().put("ChestUI", 1);
            player.openInventory(inventory);
        } catch (Exception e) {
            Util.printException(e);
        }
    }
}

ChestUIInterface.java

package com.empireminecraft.systems.chestui;

import com.empireminecraft.util.ItemUtil;
import org.bukkit.Bukkit;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.inventory.Inventory;
import org.bukkit.inventory.ItemStack;

import java.util.HashMap;

public abstract class ChestUIInterface {
    protected Player player;
    protected Inventory inventory;

    public static String getSlotLabel(int slot) {
        return "ChestUI_Slot_" + slot;
    }

    public abstract int getSize();
    public abstract String getTitle();
    public abstract void init(Player player, Inventory inventory);

    protected int slot = 0;
    protected final Inventory initialize(Player player) {
        this.player = player;
        inventory = Bukkit.createInventory(player, getSize(), getTitle());
        init(player, inventory);
        return inventory;
    }

    public Inventory getInventory() {
        return inventory;
    }

    public Player getPlayer() {
        return player;
    }

    public ChestInterfaceItem add(int slot, Material material, short data) {
        return add(slot, new ItemStack(material, 1, data));
    }
    public ChestInterfaceItem add(Material material, short data) {
        return add(slot, new ItemStack(material, 1, data));
    }
    public ChestInterfaceItem add(Material material) {
        return add(slot, new ItemStack(material));
    }
    public ChestInterfaceItem add(int slot, Material material) {
        return add(slot, new ItemStack(material));
    }
    public ChestInterfaceItem add(ItemStack item) {
        return add(slot, item);
    }
    public ChestInterfaceItem add(final int slot, ItemStack item) {
        this.slot = slot+1;
        final ChestInterfaceItem ciItem = new ChestInterfaceItem(player, inventory, slot, item);
        final HashMap<String, Object> meta = inventory.getMeta();
        meta.put(getSlotLabel(slot), ciItem);
        return ciItem;
    }
}

ConfirmChestInterface.java

package com.empireminecraft.systems.chestui;

import com.empireminecraft.util.ItemUtil;
import com.empireminecraft.util.Util;
import com.google.common.base.Predicate;
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.inventory.Inventory;

import javax.annotation.Nullable;

public class ConfirmChestInterface extends ChestUIInterface {

    private final String confirmTitle;
    private final Predicate<Player> onConfirm;
    private final Predicate<Player> onCancel;
    private final String[] lines;


    public ConfirmChestInterface(String confirmTitle, Predicate<Player> onConfirm, String... lines) {
        this(confirmTitle, onConfirm, null, lines);
    }

    public ConfirmChestInterface(
        String confirmTitle, Predicate<Player> onConfirm, Predicate<Player> onCancel, String... lines) {
        this.confirmTitle = confirmTitle;
        this.onConfirm = onConfirm;
        this.onCancel = onCancel;
        this.lines = lines;
    }

    @Override
    public int getSize() {
        return 9;
    }

    @Override
    public String getTitle() {
        return ChatColor.stripColor(Util.color(confirmTitle));
    }

    @Override
    public void init(final Player player, Inventory inventory) {
        final ItemUtil.LoreBuilder builder = add(Material.PAPER)
            .setName(confirmTitle);

        if (lines != null) {
            for (String line : lines) {
                builder.add(line);
            }
        }

        builder
            .empty()
            .add("&eClick on the &2Green Wool&e to confirm.")
            .add("&eClick on the &4Red Wool&e to cancel.")
            .save();

        add(3, Material.WOOL, (short) 13)
            .onClick(new Predicate<Player>() {
                @Override
                public boolean apply(@Nullable Player input) {
                    player.closeInventory();
                    return onConfirm.apply(input);
                }
            })
            .setName("&2Confirm")
            .add("&2Click to Confirm")
            .save();

        add(5, Material.WOOL, (short) 14)
            .onClick(new Predicate<Player>() {
                @Override
                public boolean apply(@Nullable Player input) {
                    player.closeInventory();
                    return onCancel == null || onCancel.apply(input);
                }
            })
            .setName("&4Cancel")
            .add("&4Click to Cancel")
            .save();

    }
}

ServerSwitcher.java

package com.empireminecraft.systems.chestui;

import com.empireminecraft.config.EmpireServer;
import com.empireminecraft.util.ItemUtil;
import com.empireminecraft.util.Util;
import com.google.common.base.Predicate;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.inventory.Inventory;

import javax.annotation.Nullable;

public class ServerSwitcher extends ChestUIInterface {

    @Override
    public int getSize() {
        return 27;
    }

    @Override
    public String getTitle() {
        return "Server Switcher";
    }

    @Override
    public void init(Player player, Inventory inventory) {
        addServer(Material.WOOL, 0, EmpireServer.SMP1, "This is a Survival Server");
        addServer(Material.WOOL, 1, EmpireServer.SMP2, "This is a Survival Server");
        addServer(Material.WOOL, 2, EmpireServer.SMP3, "This is a Survival Server");
        addServer(Material.WOOL, 3, EmpireServer.SMP4, "This is a Survival Server");
        addServer(Material.WOOL, 4, EmpireServer.SMP5, "This is a Survival Server");
        addServer(Material.WOOL, 5, EmpireServer.SMP6, "This is a Survival Server");
        addServer(Material.WOOL, 6, EmpireServer.SMP7, "This is a Survival Server");
        addServer(Material.WOOL, 7, EmpireServer.SMP8, "This is a Survival Server");
        addServer(Material.WOOL, 8, EmpireServer.SMP9, "This is a Survival Server");

        addServer(Material.GOLD_BLOCK, 0, EmpireServer.UTOPIA, "This is a Survival Server for", "Gold and Diamond Supporters");

        if (Util.isModerator(player)) {
            addServer(Material.FIREWORK, 0, EmpireServer.GAMES, "This is a Games Server");
            addServer(Material.TNT, 0, EmpireServer.STAGE, "This is a Test Server");
        }

    }

    void addServer(Material mat, int id, final EmpireServer server, String... extra) {
        final ItemUtil.LoreBuilder loreBuilder = add(mat, (short) id)
            .onClick(new Predicate<Player>() {
                @Override
                public boolean apply(@Nullable Player input) {
                    server.sendPlayerToServer(input);
                    return true;
                }
            })
            .setName("&bSwitch to: &a" + server.extraLabel);

        if (extra != null) {
            for (String ex : extra) {
                loreBuilder.add("&b" + ex);
            }

            loreBuilder.empty();
        }
        loreBuilder.add("&aCommand: &f/" + server.label).save();
    }
}