List example

[Dick Summerfield]

Hi all,
Here's the code for a List example taken from Just Java 2 Fifth Edition (that's the one that handles JDK 1.4 release) p. 460:

import java.util.*;
 
interface CardConsts
{
    final String[] deck =
    {
        "spd_ace", "spd_king","spd_queen", "spd_jack",
        "spd_10", "spd_09", "spd_08", "spd_07", "spd_06", "spd_05", "spd_04", "spd_03", "spd_02",
 
        "hrt_ace", "hrt_king","hrt_queen", "hrt_jack",
        "hrt_10", "hrt_09", "hrt_08", "hrt_07", "hrt_06", "hrt_05", "hrt_04", "hrt_03", "hrt_02",
 
        "clb_ace", "clb_king","clb_queen", "clb_jack",
        "clb_10", "clb_09", "clb_08", "clb_07", "clb_06", "clb_05", "clb_04", "clb_03", "clb_02",
 
        "dmd_ace", "dmd_king","dmd_queen", "dmd_jack",
        "dmd_10", "dmd_09", "dmd_08", "dmd_07", "dmd_06", "dmd_05", "dmd_04", "dmd_03", "dmd_02",
    };
}
 
public class Hand implements CardConsts
{
    Collection coll = new LinkedList();
 
    public Hand(String c[])
    {
        for ( int i = 0; i < c.length; i++ )
        {
            coll.add( c[ i ] );
        }
    }
 
    public static void main(String[] args)
    {
        String[] example =
        {
            "spd_king", "dmd_10", "clb_09", "spd_king",
        };
 
        Hand h = new Hand( example );
 
        System.out.println( "list: " + h.coll );
    }
}

The author says: "we write an interface that has constants for the suit and rank of each card ... a class that holds four cards, inherits these constants by implementing the interface.

The example works fine and I've learnt a lot about Collections from expanding this example, but what's the point of that interface. If I delete the whole goldurn thing the program works just as well!!!
Can somebody please explain this?
I'm sure I must be missing something...
[ January 20, 2008: Message edited by: Dick Summerfield ]

[Paul Santa Maria]

Hi -

No, you're not missing anything.

On pg 460, Mr. van der Linden says:

"[class 'Hand'] .. inherits these constants by implementing the interface."

But then he never bothers using any of the constants he went to the trouble of inheriting - he just declares some new constants, in String[] "example".

Great book; poor example.

'Hope that helps .. PSM

[Dick Summerfield]

Originally posted by Paul Santa Maria:
No, you're not missing anything.
... he never bothers using any of the constants he went to the trouble of inheriting - Great book; poor example.
'Hope that helps .. PSM

It certainly did, Paul - Thanks
I changed the code as follows:

String[] example =
{
    // "spd_king", "dmd_10", "clb_09", "spd_king",
    deck[1],deck[43],deck[31],deck[1],
};

... which I think illustrates the point, though I'd want to make it more readable somehow for everyday use
[ January 20, 2008: Message edited by: Dick Summerfield ]