---Small singleton class I use for most of the game modes I make---

public class Arena {
    private static Arena arena = new Arena();
    public Arena(){}
    public static Arena getArena(){
        return arena;
    }
    public boolean inGame;
    public List<Player> players;
    public List<Player> spectators;
    public HashMap<Player,Integer> kills;
    public int border;

    public boolean isInGame() {
        return inGame;
    }
    public void setInGame(boolean inGame) {
        this.inGame = inGame;
    }

    public List<Player> getPlayers() {
        return players;
    }

    public void setPlayers(List<Player> players) {
        this.players = players;
    }

    public void addPlayer(Player p){
        players.add(p);
        kills.put(p,0);
    }
    public void removePlayer(Player p){
        players.remove(p);
        kills.remove(p);
    }
    public void addSpectator(Player p){
        spectators.add(p);
    }
    public void removeSpectator(Player p){
        spectators.remove(p);
    }

    public List<Player> getSpectators() {
        return spectators;
    }

    public void setSpectators(List<Player> spectators) {
        this.spectators = spectators;
    }

    public HashMap<Player, Integer> getKills() {
        return kills;
    }

    public void setKills(HashMap<Player, Integer> kills) {
        this.kills = kills;
    }

    public Integer getPlayerKills(Player p){
       return kills.get(p);
    }
    public void setPlayerKills(Player p, Integer playerKills){
        kills.put(p,playerKills);
    }

    public int getBorder() {
        return border;
    }

    public void setBorder(int border) {
        this.border = border;
    }
}

--- This is a small plugin that will perform a command thats on a sign when you right click an armorstand---

public class main extends JavaPlugin implements Listener {

    @Override
    public void onEnable() {this.getServer().getPluginManager().registerEvents(this, this);}

    @EventHandler
    public void clickEvent(PlayerInteractAtEntityEvent e) {
        Player p = e.getPlayer();
        Entity b = e.getRightClicked();

        if (b.getType() == EntityType.ARMOR_STAND) {
            Location bLoc = b.getLocation();
            int x = bLoc.getBlockX();
            int z = bLoc.getBlockZ();
            int y1 = bLoc.getBlockY();
            int y2 = y1 - 2;
            World w = bLoc.getWorld();
            Location sLoc = new Location(w, x, y2, z);
            Block sign = sLoc.getBlock();

            if (sign.getType() == Material.SIGN || sign.getType() == Material.SIGN_POST || sign.getType() == Material.WALL_SIGN) {

                Sign signS = (Sign) sign.getState();
                String command = signS.getLine(0);
                p.performCommand(command);
            }
        }
    }
}

---  This is a modified zombie of course it needs to be added to the game  ---

import net.minecraft.server.v1_8_R3.*;
import org.bukkit.ChatColor;
import org.bukkit.craftbukkit.v1_8_R3.CraftWorld;

import java.lang.reflect.Field;
import java.util.List;

/**
 * Created by robin on 31/12/15.
 */
public class CustomZombie2 extends EntityZombie {

    public CustomZombie2(org.bukkit.World world) {

        super(((CraftWorld)world).getHandle());

        List goalB = (List)getPrivateField("b", PathfinderGoalSelector.class, goalSelector); goalB.clear();
        List goalC = (List)getPrivateField("c", PathfinderGoalSelector.class, goalSelector); goalC.clear();
        List targetB = (List)getPrivateField("b", PathfinderGoalSelector.class, targetSelector); targetB.clear();
        List targetC = (List)getPrivateField("c", PathfinderGoalSelector.class, targetSelector); targetC.clear();

        this.goalSelector.a(0, new PathfinderGoalFloat(this));
        this.goalSelector.a(2, new PathfinderGoalMeleeAttack(this, EntityHuman.class, 1.0D, false));
        this.goalSelector.a(4, new PathfinderGoalMeleeAttack(this, EntityVillager.class, 1.0D, true));
        this.goalSelector.a(5, new PathfinderGoalMoveTowardsRestriction(this, 1.0D));
        this.goalSelector.a(6, new PathfinderGoalMoveThroughVillage(this, 1.0D, false));
        this.goalSelector.a(7, new PathfinderGoalRandomStroll(this, 5.0D));
        this.goalSelector.a(8, new PathfinderGoalLookAtPlayer(this, EntityHuman.class, 16.0F));
        this.goalSelector.a(8, new PathfinderGoalRandomLookaround(this));
        this.targetSelector.a(1, new PathfinderGoalHurtByTarget(this, true));
        this.targetSelector.a(2,new PathfinderGoalNearestAttackableTarget(this,EntityHuman.class,true));
        this.targetSelector.a(2,new PathfinderGoalNearestAttackableTarget(this,EntityVillager.class,false));
        this.setCustomName(ChatColor.GREEN+"Test Subject B");
        this.getAttributeInstance(GenericAttributes.ATTACK_DAMAGE).setValue(9);
        this.getAttributeInstance(GenericAttributes.MOVEMENT_SPEED).setValue(0.5);
        this.getAttributeInstance(GenericAttributes.maxHealth).setValue(100);


    }


    public static Object getPrivateField(String fieldName, Class clazz, Object object)
    {
        Field field;
        Object o = null;
        try
        {
            field = clazz.getDeclaredField(fieldName);

            field.setAccessible(true);

            o = field.get(object);
        }
        catch(NoSuchFieldException e)
        {
            e.printStackTrace();
        }
        catch(IllegalAccessException e)
        {
        }

        return o;
    }

}


--- MySQL class---

public class MySQL {
        private String host;
        private String user;
        private String pass;
        private String db;
        private String p;

        private Connection c;

        public MySQL (String hostName,String userName,String password, String database, String port){
            if(hostName!=null && userName!=null && password!=null && database != null){
                host=hostName;
                user=userName;
                pass=password;
                db=database;
                if(port==null){
                    p = "3306";
                }else{
                    p= port;
                }
            }
        }
        public void connect(){
            try {
                c = DriverManager.getConnection("jdbc:mysql://" + host + ":" + p + "/"
                        + db + "?autoReconnect=true", user, pass);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        public void close(){
            try {
                c.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }

        public void update(String qry) {
            try {
                Statement st = c.createStatement();
                st.executeUpdate(qry);
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        public ResultSet query(String qry) {
            ResultSet rs = null;

            try {
                Statement st = c.createStatement();
                rs = st.executeQuery(qry);
            } catch (SQLException e) {
                connect();
                System.err.println(e);
            }
            return rs;
        }

        public Connection getC() {
            return c;
        }
    }