Talk:Generics in Java

message: I removed the following text, as it isn't correct:
It is possible to work around this limitation to some extent by using Java's reflection mechanisms.  If an instance of class T is available, one can obtain from that object the Class object corresponding to T and use java.lang.reflect.Array.newInstance to create the array.
Let's say I have toArray(List<T> list) with at least one element.  I call this using a List<Number> containing Integers and Floats.  Array.newInstance() using my first element of my list (which an instance of class Number) I end up with an array of type Integer[].  When I try to add a Float to the array, my program will fail with an error.
Now, it is possible if I pass in a Class<T> as in toArray(List<T> list, Class<T> clazz).  Calling Array.newInstance(clazz, list.length()) will work just fine.  However, I don't think it's worth mentioning this in the actual article. —Matthew0028 07:50, 11 December 2006 (UTC)
thread_title: Reflection example not correct

message: This article only tells what the problems are with Java generics. It doesn't even tell you how to use any of the generic features, like the For-next loop or autoboxing. —The preceding unsigned comment was added by Ed Poor (talk • contribs) 22:30, 7 February 2007 (UTC)
replies: text: Indeed. It doesn't even define Generics. The first sentence talks about when they were added to the language, and the second goes right into comparison with C++. This article needs work. --King Mir 01:52, 13 February 2007 (UTC)

text: This article used to be part of the generic programming page (but you know that already), which provided a little more context on the subject. I agree it should at least mention how it can help with type safety (even if only to a degree) and readability (same footnote), and can prevent the need for casts. (Note that foreach and autoboxing don't really require generics, they were in the C# language before it introduced generics.) Perhaps some examples that show the good points would be nice too. - Chip Zero 15:38, 13 February 2007 (UTC)
thread_title: Anti-Java bias

message: Removed the Anti-Java Content, Added viable examples, Corrected Incorrect Example.
This is not a facility to compare Java to other languages; If a comparison is useful, it has every reason to be here.
Please take the time to remove negative/spiteful content when ever possible.
Thank you =)
:Oh, the "rules" you refer to are not part of wikipedia policies, except spitefulness, which is forbidden. First of all: please sign your postings with four tildes ',secondly: it is quite legal to compare Java to other languages here, but there are specific articles for Comparison of C# and Java, Comparison of Java and C++. Specific criticisms without comparisons. could very well be in this article, but there are certain rules: this is not a scribble board, so criticisms must be wide spread outside criticisms, and they should be verified by providing external sources. If there are prominent counterarguments on specific criticisms, it is very desirable those counterarguments are mentioned here too. Wikipedia have no opinion of its own, but it doesn't hesitate to mention important criticisms from outside, since no censorship except the encyclopedic style and layout apply here. Criticisms should be in a section called "criticism", the criticisms should be outside-citable, and the text formulations in this article should be neutral and non-inflamatory. ... said: Rursus (bork²) 15:19, 22 April 2009 (UTC)
thread_title: Anti-Java bias Updated

message: I tried to improve content of this article. We certainly have to start with relevant to this subject Java language specifications - then to go down to examples. I do not see any reason for autoboxing/unboxing section here - it has nothing to do with generics. Also, nested generics 'explained' here by an example - are simply ugly.--Stagalj (talk) 00:08, 13 February 2008 (UTC)
thread_title:  Feb 2008 edits 

message: GCJ 4.3 support all 1.5 features, including generics. I don't know where it should be written, however. And besides, I'm dying for coffee now! ... said: Rursus (bork²) 13:14, 28 April 2009 (UTC)
thread_title: GCJ

message: “Reflection can also determine the type parameter”. Come again? By what means other than “individual elements may be examined to determine the type they belong to”? --Zahnradzacken (talk) 08:39, 27 October 2010 (UTC)
thread_title:  Reflection? 

message: Most of articles on the Internet (including this one) give the reader an impression that generic type information is completely removed from the resulting bytecode when compiling Java source to .class files.
This is wrong - this information is retained on declarations of classes, methods and fields using a bytecode extensibility mechanism called "attribute". Generic type information is saved in the bytecode in the signature attribute.
Erasure of this information takes place during runtime - actual in memory class instances (objects) are unable to hold generic type information so you cannot check them during runtime. However, you can still access generic type information on methods, classes and fields using reflection API:
http://download.oracle.com/javase/1.5.0/docs/api/java/lang/reflect/GenericDeclaration.html
For detailed explanation, see this article:
http://www.ibm.com/developerworks/java/library/j-cwt02076.html
To cite a fragment: "In this article, I'll show how you can use ASM both to retrieve the raw generics information out of class files and to interpret the generics in a useful manner. Before digging into the ASM details, I'll start off with a look at how generics information is actually encoded into the binary classes." 
 
--Aleksander.adamowski (talk) 19:35, 12 January 2011 (UTC)
thread_title:  Java Bytecode representation of generics 

message: In wildcards we find "and writing non-null elements to the list is not allowed".
So it's a list with only null elements? Did you mean "and writing null elements to the list is not allowed"
57.66.70.225 (talk) 17:36, 27 January 2012 (UTC)
thread_title:  Wildcards chapter 

message: The article states "As a result, the type parameter cannot be used in the declaration of static variables or in static methods." but gives an example static method public static <T> Entry<T,T> twice(T value) earlier. So, that must be wrong? --2A01:198:285:0:250:FCFF:FEAD:B479 (talk) 16:44, 6 October 2012 (UTC)
thread_title:  static methods