Generics

[anil kumar]

public class TestWildcards {
public static void main(String[] args) {
List<Integer> myList = new ArrayList<Integer>();
Bar bar = new Bar();
bar.doInsert(myList);
}
}

class Bar {
void doInsert(List<Object> list) {
list.add(new Dog());
}
}


Now will it work? If not, why not?
This time, class Bar, with the doInsert() method, compiles just fine. The
-------------------------------------------------- -----------------
problem is that the TestWildcards code is trying to pass a List<Integer> into a
method that can take ONLY a List<Object>. And nothing else can be substituted for
<Object>.

These statements are from K&B ,see above underline words.
I think the program will not compile.

Thanks
Anil kumar
[ April 26, 2007: Message edited by: anil kumar ]

[Chandra Bhatt]

public class TestWildcards {
public static void main(String[] args) {
List<Integer> myList = new ArrayList<Integer>();
Bar bar = new Bar();
bar.doInsert(myList);
}
}
 
class Bar {
void doInsert(List<Object> list) {
list.add(new Dog());
}
}

Wont compile!
Try to pass a List parameterized with Integer to a method which only asks
for List parameterized with Object nothing else.


You can make it:

void doInsert(List<? super Integer> list) {
list.add(new Integer(5));//OK
}

Regards,
cmbhatt
[ April 26, 2007: Message edited by: Chandra Bhatt ]

[anil kumar]

Hi
Chandra
Thanks
ya it will not work.

But i have seen and i think it is not included in errata.My be for them it is a minor mistake.

Thanks
Anil kumar

[Barry Gaunt]

This time, class Bar, with the doInsert() method, compiles just fine.

Why won't class Bar compile fine?

It tells you why class TestWildcards does not compile - not class Bar.
[ April 26, 2007: Message edited by: Barry Gaunt ]

[anil kumar]

Hi

Barry Gaunt

Thank you.