Calendar static final fields

[Pratik D mehta]

My Question is
We Create a concrete subclass instance of the Calendar Abstract Class using getInstance() method.
Than we can use add(field,amount) method to make changes to the fields in Calendar class.
But all these fields in Calendar class are static final , and how can we make changes to static final fields of the Calendar class.
eg -

public class NewClass1 {
public static void main(String args[])
    {
    Calendar c2 = Calendar.getInstance();
    Date d2 = new Date();
    d2 = c2.getTime();
    c2.add(Calendar.DATE,45);//DATE is a static final fied , So how can we change it .
    d2 = c2.getTime();
    System.out.println(d2);
    d2 = c2.getTime();
     System.out.println(d2);

}
}

[Al Fraelich]

reading through the API, I understand that it's certain things that are "static final" for example, number of months or names of months or number of days in a particular month. they don't want you adding the 45th of septober or something like that. Things that will never change, are best kept as "static final", speed of light, feet in a mile, JavaRanch's awesomeness and so on.

Hope that helps,
Al

[Pratik D mehta]

Al Fraelich wrote:reading through the API, I understand that it's certain things that are "static final" for example, number of months or names of months or number of days in a particular month. they don't want you adding the 45th of septober or something like that. Things that will never change, are best kept as "static final", speed of light, feet in a mile, JavaRanch's awesomeness and so on.

Hope that helps,
Al

Thats not my question Al Fraelich
My question is that I am changing the field DATE in the above example by using add(Calendar.DATE,35);
But DATE is static final .
So why is it changing , we cannot change it Right ?

[Christophe Verré]

Calendar.DATE is just an index (whose value is 5). It is used to access the date field, which is not final.

[Pratik D mehta]

I didnt get that Christophe Verré .
Can you please simplify it for me , how does it work .

[Campbell Ritchie]

If you enter 1 it alters the no 1 field; if you enter 2 it alters the no 2 field. Those numbers are hidden behind the field names DATE MONTH YEAR etc., but you can find them from Calendar#field_detail and the "Constant Field Values" link.

[Pratik D mehta]

So it it that the static final constant value of DATE gives call to Date which return the current Date .
Can you please tell me it calls which method in date to get the current date.
Have I got it right .
I think I am curious and Impatient on how things work deeply in java , Is it that I should go on reading and things would be clear gradually.
I still havent finished K & B .
Please advice me on that .
How can I proceed towards reading.

[Campbell Ritchie]

Don't know. You can find the code by unzipping the file called src.zip, which is usually inside your Java installation folder. It probably uses a switch-case block.

[Sridhar Santhanakrishnan]

This might help.

[Campbell Ritchie]

Sridhar Santhanakrishnan wrote:This might help.

Yes, it did.

[Pratik D mehta]

Thanyou Campbell and Sridhar