code: @Override
      public int compareTo(ExchangeRate o) {
          Objects.requireNonNull(o);
          int compare = this.getBaseCurrency().getCurrencyCode().compareTo(o.getBaseCurrency().getCurrencyCode());
          if (compare == 0) {
              compare = this.getCurrency().getCurrencyCode().compareTo(o.getCurrency().getCurrencyCode());
          }
          if (compare == 0) {
              compare = this.getContext().getProviderName().compareTo(o.getContext().getProviderName());
          }
          return compare;
      }
docs: /*
  (non-Javadoc)
  
  @see java.lang.Comparable#compareTo(java.lang.Object)