L2J Server

hi i would like to ask you how can i make a npc to hit only specific players like karma guards.

i coded this but i do not know if it is right:

for (L2Npc monster : _monsters)
{
((L2Attackable) monster).addDamageHate(X,9000,9000);
monster.getAI().setIntention(CtrlIntention.AI_INTENTION_ATTACK, X, null);
}

_monsters are specific monsters and x should be the character

now i do not know how to make the X to be a player which is noblesse.

any ideas?