class Bond {

	Bond(Atom from, Atom to, int order) {
		if (from == to){
			throw new IllegalArgumentException("Bonds must be made between different atoms");
		}
		if (order < 1 || order > 3){
			throw new IllegalArgumentException("Bond order must be 1, 2 or 3");
		}
		if (from == null){
			throw new IllegalArgumentException("From atom was null!");
		}
		if (to == null){
			throw new IllegalArgumentException("To atom was null!");
		}
		this.from = from;
		this.to = to;
		this.order = order;
	}

	  Bond(Atom from, Atom to, int order);

}