public synchronized void addStation(String alias) {
		Iterator<String> it = stations.iterator();
		for(int i = 0; i < stations.size(); i++) {
			// compare both strings
			int com = it.next().compareTo(alias);
			if(com == 0) {
				throw new IllegalStateException("The alias " + alias + " is already part of this network.");
			} else if(com > 0) {
				stations.add(i, alias);
				return;
			}
		}
		// In case no other condition triggered
		stations.add(alias);
	}