Do we have a Readonly field in java (which is set-able within the scope of the class itself)?

Create a class with public final fields. Provide constructor where those fields would be initialized. This way your class will be immutable, but you won’t have an overhead on accessing the values from the outside. For example:

public class ShortCalendar
{
    public final int year, month, day;

    public ShortCalendar(Calendar calendar)
    {
        if (null == calendar)
            throw new IllegalArgumentException();

        year = calendar.get(Calendar.YEAR);
        month = calendar.get(Calendar.MONTH);
        day = calendar.get(Calendar.DATE);
    }
}