code: public void setCurrencyUsage(CurrencyUsage newUsage) {
          if (newUsage == null) {
              throw new NullPointerException("return value is null at method AAA");
          }
          currencyUsage = newUsage;
          Currency theCurrency = this.getCurrency();
  
          // We set rounding/digit based on currency context
          if (theCurrency != null) {
              setRoundingIncrement(theCurrency.getRoundingIncrement(currencyUsage));
              int d = theCurrency.getDefaultFractionDigits(currencyUsage);
              setMinimumFractionDigits(d);
              _setMaximumFractionDigits(d);
          }
      }
docs: Sets the <tt>Currency Usage</tt> object used to display currency.
  This takes effect immediately, if this format is a
  currency format.
  @param newUsage new currency context object to use.