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Generic Question

Sagar Shroff
Ranch Hand

Joined: Jun 07, 2011
Posts: 209

Can some one make me explain why this is not compiling.The compiler is telling me that Parameter is not within Bounds......

Also not understanding then how this is working ??

Please Help me ??

Examples would be really appreciated !!

Can someone please help me with an example of my 2 Questions ??

Ankit Garg

Joined: Aug 03, 2008
Posts: 9453

In this case you are declaring a new K with your method declaration. Basically the code is equivalent to this code

Now here M might be resolved to something not compatible with Number, like lets say String. But Test class can only have a type which is a Number. So you'll have to bound M to a number.

Here first of all the type declaration in the method is useless. So we'll strip it out first

Now the return type would clearly work. As for the parameter, since you are using a wildcard syntax, so compile would be able to maintain type safety here. Lets actually put some code into the class to see how

Basically you can't make changes to s variable based on its type as the type is not known. So even though ? super K seems to be breaking the bounds of K, it will still result in type safe code which is the goal of generics...

SCJP 6 | SCWCD 5 | Javaranch SCJP FAQ | SCWCD Links
Sagar Shroff
Ranch Hand

Joined: Jun 07, 2011
Posts: 209

Thanks Ankit !!
I agree. Here's the link:
subject: Generic Question
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