public void newNPCDrop(int npcType, int dropType, int Items[], int ItemsN[]) {
		// first, search for a free slot
		int slot = -1;
		for (int i = 0; i < maxNPCDrops; i++) {
			if (NpcDrops[i] == null) {
				slot = i;
				break;
			}
		}

		if(slot == -1) return;		// no free slot found

		NPCDrops newNPCDrop = new NPCDrops(npcType);
		newNPCDrop.DropType = dropType;
		newNPCDrop.Items = Items;
		newNPCDrop.ItemsN = ItemsN;
		NpcDrops[slot] = newNPCDrop;
	}