protected Field(String name,
    int calendarField) 
{
            super(name);
            this.calendarField = calendarField;
            if (this.getClass() == DateFormat.Field.class) {
                instanceMap.put(name, this);
                if (calendarField  >= 0) {
                    // assert(calendarField <  Calendar.FIELD_COUNT);
                    calendarToFieldMapping[calendarField] = this;
                }
            }
}

Creates a Field.

Parameters:

name - the name of the Field

calendarField - the Calendar constant this Field corresponds to; any value, even one outside the range of legal Calendar values may be used, but -1 should be used for values that don't correspond to legal Calendar values

 public int getCalendarField() 
{
            return calendarField;
}

Returns the Calendar field associated with this attribute. For example, if this represents the hours field of a Calendar, this would return Calendar.HOUR. If there is no corresponding Calendar constant, this will return -1.

 public static Field ofCalendarField(int calendarField) 
{
            if (calendarField <  0 || calendarField  >=
                        calendarToFieldMapping.length) {
                throw new IllegalArgumentException("Unknown Calendar constant "
                                                   + calendarField);
            }
            return calendarToFieldMapping[calendarField];
}

Returns the Field constant that corresponds to the Calendar constant calendarField. If there is no direct mapping between the Calendar constant and a Field, null is returned.

 protected Object readResolve() throws InvalidObjectException 
{
            if (this.getClass() != DateFormat.Field.class) {
                throw new InvalidObjectException("subclass didn't correctly implement readResolve");
            }
            Object instance = instanceMap.get(getName());
            if (instance != null) {
                return instance;
            } else {
                throw new InvalidObjectException("unknown attribute name");
            }
}

Resolves instances being deserialized to the predefined constants.