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Wild card generic type

nitin pokhriyal
Ranch Hand

Joined: May 19, 2005
Posts: 263
I was going through the tutorials i saw

ArrayList<?> coll1 = new ArrayList <?> (); // error

will not compile but i am able to compile it. Please advice where i am wrong?
Manfred Klug
Ranch Hand

Joined: Jun 04, 2007
Posts: 377
Originally posted by nitin pokhriyal:
but i am able to compile it.

Interesting. For me, compilation fails.
Christophe Verré
Sheriff

Joined: Nov 24, 2005
Posts: 14688
    
  16

Please advice where i am wrong?

You're compiling the wrong class ?


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nitin pokhriyal
Ranch Hand

Joined: May 19, 2005
Posts: 263
Strange thing if i am trying to compile it wil Jdeveloper it will compile fine for me but if i try to use jdevelopers jdk in comand prompt i got

1. B.java:8: unexpected type
2. found : ?
3. required: class or interface without bounds
4. ArrayList<?> arr=new ArrayList<?>();


^
Chandra Bhatt
Ranch Hand

Joined: Feb 28, 2007
Posts: 1707


I don't see anything wrong here!


Thanks,


cmbhatt
nitin pokhriyal
Ranch Hand

Joined: May 19, 2005
Posts: 263
Chandra bhatt,

That is what i am not getting from jdeveloper but when i try to compile from command prompt i got error.
Barry Gaunt
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Joined: Aug 03, 2002
Posts: 7729
Originally posted by Chandra Bhatt:


I don't see anything wrong here!


Thanks,


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nitin pokhriyal
Ranch Hand

Joined: May 19, 2005
Posts: 263
that is the reference material i refered but y chandra is not getting error even if i use jdeveloper i am also not getting that error as i explained in my previous post.
Chandra Bhatt
Ranch Hand

Joined: Feb 28, 2007
Posts: 1707
Ooops!
I missed that.

Thanks Barry



It wont compile. While constructing an parameterized object, you must give
it a type that is actual object and not wildcard. You can use wildcard
parameterized type with ref variable not object type.
 
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subject: Wild card generic type