public String toString() {
		String str = "[";
		for (int i = 0; i < structure.length; i++) {

			if (structure[i] != null)
				str += structure[i].toString() + " , ";

		}
		str = str.substring(0, str.length() - 3);
		str += "] count: " + structure.length;
		return str;
	}