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generics...

Preethi Dev
Ranch Hand

Joined: Sep 07, 2008
Posts: 265
Hi ,i am just trying to understand the concept of generics and this is my own.


import java.util.*;
class card
{

public static void main(String args[])
{

card[] pair=new card<?,?>[10];
pair[0]=new card<Long,Long>(0L,0L);
pair[1]=new card<String,String>("","");
pair[2]=new card<String>("");

}
}
here i am getting compiler errors as "type card does not take parameters for each line in the main method".
should i create constructor for card?
if so how can i create it for unbounded wildcard parameterized type?

please clear this...

Thanks
Preetha
Chandra Bhatt
Ranch Hand

Joined: Feb 28, 2007
Posts: 1707
Hi Preetha,

What do you want to achieve here?
Generic array creation is not allowed.


cmbhatt
Punit Singh
Ranch Hand

Joined: Oct 16, 2008
Posts: 952
import java.util.*;
public class card<T,E>
{

public card(T obj1, E obj2){

}

public card(T obj1){

}
public static void main(String args[])
{

card[] pair=new card[10];
pair[0]=new card<Long,Long>(0L,0L);
pair[1]=new card<String,String>("","");

}
}

You have to make generic card class.
[ December 07, 2008: Message edited by: Punit Singh ]

SCJP 6
Preethi Dev
Ranch Hand

Joined: Sep 07, 2008
Posts: 265
Hi Chandra,
It is allowed to create an array whose component type is an unbounded wildcard parameterized type.
just go through this www.angelikalanger.com

Thanks
Preetha
Deepak Jain
Ranch Hand

Joined: Aug 05, 2006
Posts: 637
Yes you should
Two Fixes:
Non Generic Code:


Generic Code: This shows generics are power full


Card[] pair = new Card<?,?>[10];
This line says that the array pair can take objects of any type . Since we have ? ? [2 ?] this implies that the objects must have a constructor that can take 2 arguments.


SCJP, SCWCD, SCBCD
Preethi Dev
Ranch Hand

Joined: Sep 07, 2008
Posts: 265
Thanks Deepak,

i tried with constructor it works.

Preetha
 
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