code: public void setCurrency(Currency currency) {
          if (currency == null) {
              throw new NullPointerException();
          }
          this.currency = currency;
          intlCurrencySymbol = currency.getCurrencyCode();
          currencySymbol = currency.getSymbol(locale);
          //cachedIcuDFS = null;
      }
docs: Sets the currency of these DecimalFormatSymbols.
  This also sets the currency symbol attribute to the currency's symbol
  in the DecimalFormatSymbols' locale, and the international currency
  symbol attribute to the currency's ISO 4217 currency code.
  
  @param currency the new currency to be used
  @exception NullPointerException if <code>currency</code> is null
  @since 1.4
  @see #setCurrencySymbol
  @see #setInternationalCurrencySymbol