code: private void initLocalZeroPaddingNumberFormat() {
          if (numberFormat instanceof DecimalFormat) {
              decDigits = ((DecimalFormat)numberFormat).getDecimalFormatSymbols().getDigits();
              useLocalZeroPaddingNumberFormat = true;
          } else if (numberFormat instanceof DateNumberFormat) {
              decDigits = ((DateNumberFormat)numberFormat).getDigits();
              useLocalZeroPaddingNumberFormat = true;
          } else {
              useLocalZeroPaddingNumberFormat = false;
          }
  
          if (useLocalZeroPaddingNumberFormat) {
              decimalBuf = new char[DECIMAL_BUF_SIZE];
          }
      }
docs: /*
  Initializes transient fields for fast simple numeric formatting
  code. This method should be called whenever number format is updated.