如何使用上下文在Spring Batch中将最终变量设置为全局变量？

Question

ItemReader<Token> tokenReader(DataSource dataSource) {
    DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
    DateFormat dfFileName = new SimpleDateFormat("MM_dd_yyyy");
    Calendar startDateCal = Calendar.get Instance();
    startDateCal.add(Calendar.DAY_OF_MONTH, -Integer.parseInt(env.getProperty("runForNoOfDays")));
    startDateCal.set(Calendar.HOUR, 0);
    startDateCal.set(Calendar.MINUTE, 0);
    startDateCal.set(Calendar.SECOND, 0);
    final String startDateStr = dateFormat.format(startDateCal.getTime());
}

我想将最终String startDateStr声明为全局。我可以使用哪些方法？