docs: private static DecimalFormatSymbols setSymbolAndCode(DecimalFormat numberFormat, String symbol, String code) {
          checkState(Thread.holdsLock(numberFormat));
          DecimalFormatSymbols fs = numberFormat.getDecimalFormatSymbols();
          DecimalFormatSymbols ante = (DecimalFormatSymbols)fs.clone();
          fs.setInternationalCurrencySymbol(code);
          fs.setCurrencySymbol(symbol);
          numberFormat.setDecimalFormatSymbols(fs);
          return ante;
      }