@Override public int compareTo(ExchangeRate o) { if (o == null) { return -1; } int compare = ((Comparable<ExchangeRateType>) this.getExchangeRateType()) .compareTo(o.getExchangeRateType()); if (compare == 0) { if (provider != null) { compare = this.provider.compareTo(o.getProvider()); } else if (o.getProvider() != null) { compare = o.getProvider().compareTo(this.provider); } } return compare; }