Exp Convert Plugin

package xp;

import org.bukkit.Bukkit;
import org.bukkit.Material;
import org.bukkit.entity.EntityType;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;
import org.bukkit.plugin.java.JavaPlugin;
public class xp extends JavaPlugin implements Listener {

    public void onEnable(){
        Bukkit.getPluginManager().registerEvents(this,this);
    }
    public void onDisable(){

    }
    @EventHandler
    public static void ConvertXP(PlayerInteractEvent e)
    {
        Player p=e.getPlayer();
        String nameXpWand="§4Палка-починялка";
        ItemStack xpWand=new ItemStack(Material.STICK,1);
        ItemMeta xpWandMeta=xpWand.getItemMeta();
        xpWandMeta.setDisplayName(nameXpWand);
        xpWand.setItemMeta(xpWandMeta);
        if(e.getItem().getItemMeta().getDisplayName().equals(nameXpWand)){
            if(p.getLevel()>=20)
            {
                int xpOnLevel=(int)(p.getExp()*p.getExpToLevel());
                if(xpOnLevel>10)
                    p.giveExp(-10);
                else
                    if(xpOnLevel==10){
                        p.setExp(0);
                    }
                    else
                        if(xpOnLevel<10){
                            int num=10-xpOnLevel;
                            p.setExp(0.0f);
                            p.setLevel(p.getLevel()-1);
                            float newXp=((float)(p.getExpToLevel()-num)/(float)p.getExpToLevel());
                            p.setExp(newXp);
                        }
                p.getWorld().spawnEntity(p.getLocation(), EntityType.THROWN_EXP_BOTTLE);
            }
        }
    }
}