AnvilDrop.java

package me.rwd.funevents.items;

import org.bukkit.ChatColor;
import org.bukkit.Location;
import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.*;

/**
 * Created by George on 06-Dec-16.
 * Distribution of thise code is forbidden unless
 * permission is granted. Any code on Github is
 * primarily for learning purposes. Please msg
 *
 * @Rapidwolf_ on twitter for information
 */
public class AnvilDrop extends CustomItem {
    @Override
    protected ItemDefinition getItemDefinition() {
        return new ItemDefinition(Material.STICK, ChatColor.RED + "" + ChatColor.BOLD + "Anvildrop");
    }

    @Override
    public Recipe getRecipe() {
        ShapedRecipe recipe = new ShapedRecipe(getItemStack());
        recipe.shape(
                "III",
                "IAI",
                "III"
        );
        recipe.setIngredient('I', Material.IRON_BLOCK);
        recipe.setIngredient('A', Material.ANVIL);
        return recipe;
    }

    @Override
    public void onUse(Player player) {
        Location spawnLoc = player.getLocation().add(0, 10, 0);
        spawnLoc.getBlock().setType(Material.ANVIL);
    }
}

CustomItem.java

package me.rwd.funevents.items;

import org.bukkit.Material;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.Recipe;
import org.bukkit.inventory.meta.ItemMeta;
import org.bukkit.material.MaterialData;

public abstract class CustomItem {
    public ItemStack getItemStack() {
        ItemDefinition itemDef = getItemDefinition();
        ItemStack item = itemDef.mat.toItemStack();
        ItemMeta meta = item.getItemMeta();
        meta.setDisplayName(itemDef.name);
        item.setItemMeta(meta);
        return item;
    }

    protected abstract ItemDefinition getItemDefinition();

    public abstract Recipe getRecipe();

    public abstract void onUse(Player player);

    protected class ItemDefinition {
        public final MaterialData mat;
        public final String name;

        public ItemDefinition(MaterialData mat, String name) {
            this.mat = mat;
            this.name = name;
        }

        public ItemDefinition(Material mat, String name) {
            this.mat = new MaterialData(mat);
            this.name = name;
        }
    }
}

CustomItemListener.java

package me.rwd.funevents.items;

import com.google.common.collect.Maps;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.EquipmentSlot;
import org.bukkit.inventory.ItemStack;

import java.util.Collection;
import java.util.Map;

import static me.rwd.funevents.utils.ItemUtils.*;

public class CustomItemListener implements Listener {
    private final Map<Integer, CustomItem> customItems;

    public CustomItemListener(Collection<CustomItem> items) {
        this.customItems = Maps.uniqueIndex(items, item -> hashItemStack(item.getItemStack()));
    }

    @EventHandler
    public void onUseItem(PlayerInteractEvent e) {
        if(! e.getHand().equals(EquipmentSlot.HAND))
            return;

        ItemStack inHand = e.getItem();
        CustomItem customItem = customItems.get(hashItemStack(inHand));
        if(customItem == null)
            return;

        customItem.onUse(e.getPlayer());
    }
}