Store an Calendar in constant field to use it later avoiding create it inside the method

Question

Is there any problem with below code?

I want to use the method parseDateToInteger in a process that execute million times. This process can be accessed in multithread way, so I synchronized the method. I avoid to create the Calendar instance inside the method, cause its take a precious time. But I don't sure about this code behaviour. There are any problem in use this code?

private static final Calendar CALENDAR_BRASIL = GregorianCalendar.getInstance(LOCALE_BRASIL);


public synchronized static int parseDateToInteger(Date data) {
    CALENDAR_BRASIL.setTime(data);
    int ano = CALENDAR_BRASIL.get(Calendar.YEAR);
    int mes = CALENDAR_BRASIL.get(Calendar.MONTH)+1;
    int dia = CALENDAR_BRASIL.get(Calendar.DATE);
    return ano * 10000 + mes * 100 + dia;       
}

EDIT: I See this article that makes me afraid, but the author don't used a synchronized method.

http://blog.bielu.com/2008/08/javautilcalendar-confusion-is-it-safe_28.html

Answer 1

This is a bad idea. Although you've avoided creating all of those objects, you now have a method that can only be used by one object at a time. So instead of creating a million objects, partially in parallel, you're going to have processes that have to wait their turn to use the Calendar.

Just create the instance for each thread.