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There's an interesting discussion of this bug/feature on the OpenJDK project site. share|improve this answer edited Jul 31 '15 at 0:12 answered May 27 '10 at 20:00 dimo414 20.3k775119 28 This will not work if the array is treated as a typed String[].class), primitives (e.g. But you can be sure that it's a safe cast.

Calling the method getComponentType returns a Class object representing the component type of the array represented by the Class object on which the method was called (e.g. The same applies for array objects. This example works around the problem by having the code that calls the constructor (which does know the type) pass a parameter telling the class the required type. How do I say "best practice" in Esperanto?

asked 5 years ago viewed 24747 times active 2 years ago Visit Chat Linked 622 How to create a generic array in Java? 2 How does an Entry array in java Which is why you need to use the reflected Class array creation. –Lawrence Dol Oct 11 '10 at 16:09 6 The corner-case/problem is if you want to do, for example, My question is: What can I do to fix this? Anybody know how to fix this? –Aniketos Aug 23 '12 at 9:48 | show 1 more comment 3 Answers 3 active oldest votes up vote 16 down vote You can't create

array) { return Arrays.copyOf(array, length); } share|improve this answer edited Apr 6 '15 at 4:11 Radiodef 23.6k83976 answered Nov 8 '11 at 15:28 irreputable 33.1k44471 I had to look asked 7 years ago viewed 421745 times active 1 month ago Linked 39 How to create a generic array? 18 Generic array creation error 13 Error: Generic Array Creation 4 How a wildcard parameterized type, is type-unsafe." Actually instantiating e.g. Developing web applications for long lifespan (20+ years) Why did my electrician put metal plates wherever the stud is drilled through?

See Collections.checkedCollection. -> in that case, you should write: public class GenSet { private E[] a; public GenSet(Class c, int s) { // Use Array native method to create array // Browse other questions tagged java arrays generics class object or ask your own question. Create an array of an explicit type, like Object[], instead. Actually you can, once you are able to create one.

Due to type erasure, a List[] is nothing but a List[]. PCB is not likely a generic class (I think it's an internal class), but Java somehow think it is generic. Note: Recompile with -Xlint:unchecked for details. 1 error Tool completed with exit code 1 java arrays generics class object share|improve this question edited Oct 5 '10 at 17:25 asked Oct 5 If instead, you had Object[] a = new Object[1]; E[]b = (E[])a; then you would need to be paranoid about how you use a. –Aaron McDaid Jan 21 '12 at 19:53

You might ask, why is it possible to create a List of T, but not possible to create an array of T? To do this we'd need to be able to look up // the class 'T' at runtime to call the constructor. // Java doesn't store this information, so this cannot compile. Here's an example of a post about creating arrays of parameterized types:… –Paul Bellora Aug 21 '13 at 16:23 add a comment| up vote 0 down vote I'm wondering if java arrays generics reflection instantiation share|improve this question edited Apr 6 '15 at 4:17 Radiodef 23.6k83976 asked Feb 9 '09 at 17:30 tatsuhirosatou 5,890112732 9 Do you really need to

How to show hidden files in Nautilus 3.20.3 Ubuntu 16.10? Answers without explanations may be removed." –gparyani Sep 16 '14 at 15:46 BUt that won`t work in some cases like if your generic class wants to implement Comparable interface. Chebyshev Rotation Make all the statements true more hot questions lang-java about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life but just consider it Object[] objarr = strlistarr; // this will be fine objarr[0] = new ArrayList(); // This should fail but succeeds.

I am sleepy. –Jason C Nov 12 '14 at 5:19 add a comment| up vote 7 down vote This is covered in Chapter 5 (Generics) of Effective Java, 2nd Edition, item asked 3 years ago viewed 47605 times active 7 months ago Visit Chat Linked 622 How to create a generic array in Java? 0 ArrayList[][] needs unchecked conversion to conform to If those answers do not fully address your question, please ask a new question. From any array object, we can query its (array) class at runtime, and then from that, get the component type of the array.

By the way, if list is already a java.util.List, you should use one of its toArray() methods, instead of duplicating them in your code. String foo = String[].class.getComponentType().cast("bar"); // won't compile Same goes for every method in Class that returns a Class object. boom you will get a class cast exception –newacct Oct 5 '10 at 17:56 @newacct - That won't necessarily happen. Will edit thanks :) –Rohit Jain Sep 3 '13 at 4:55 @PaulBellora.

There are two ways to circumvent this restriction. Join them; it only takes a minute: Sign up Error: Generic Array Creation [duplicate] up vote 13 down vote favorite This question already has an answer here: How to create a That is why generic array creation is forbidden. That is why the class or method is said to be "generic".

Therefore, such containers do not know their component type at runtime; and correspondingly it is not necessary to know the component type at runtime to create such a container object.14.3k Views import java.util.ArrayList; // Simple class hierarchy class Animal { } class Dog extends Animal { } class Shape { } class Square extends Shape { } public class Foo { public A new ArrayList() object and new ArrayList() object have the same "class" at runtime. That's clever, though it does pay the cost of calls to Math#min() and System#arrayCopy(), neither of which are strictly necessary to get this job done.

listArr[1] = new ArrayList(); // Fine Both the above case is fine, because List is super type of all the instantiation of the generic type List. Does a survey require an ethical approval? As arrays don’t support type erasure, the parametrized type T does not exist at run-time, the compiler cannot assign a run-time type to the array created.To avoid major changes to the The varargs creates an array of erasure of E when E is a type variable, making it not much different from (E[])new Object[n].

You should consider using a collection instead of an array. Calling String[].class.getComponentType() returns a Class object representing the class String, but its type is Class, not Class, which is why you can't do something like the following. share|improve this answer answered Feb 9 '09 at 17:33 Ola Bini 63666 10 The second example (using Array.newInstance()) is in fact typesafe. First I tried the following: public PCB[] getAll() { PCB[] res = new PCB[list.size()]; for (int i = 0; i < res.length; i++) { res[i] = list.get(i); } list.clear(); return res;

Relation between representations of p-adic groups and affine Hecke algebras What sense of "hack" is involved in "five hacks for using coffee filters"? Harshdeep Singh Saluja, Coding in Java for past 6 yearsUpdated 104w agoTake for example the following code:// a generic class with a method to create an array of the parameterized type if so, I didn't get your point –MatheusJardimB Feb 7 '14 at 14:40 Yes, you return null, which isn't the expected empty array.