I'm a tad confused. Why are you going through all the trouble to
make this work? The last post Aeon asked about hand hacking the
compiled class files. That sounds pretty desperate. Isn't there
some other way to code things to get at the functionality you need?
Can anyone enlighten me?
Regards,
Aaron R>
On 12/13/06, Aeon B. C. Lee <email@hidden > wrote:
Yes, you have nailed it.
So if I remove the checkcast instructions, the code will be just
fine. Do you know any handy tool to edit the compiled class file?
Thanks, Aeon
On Dec 13, 2006, at 10:49 AM, Jerry wrote:
Hi,
Yes, I agree that it's a bug. I think the problem is that the
function definition and its call are both fine in isolation, but
not when put together (and I'm glad that I don't have to try and
write the code which would spot this at compile time). The
annoying thing is that if the compiler didn't issue the
checkcast instruction at the end of your function, I think the
code would work fine. The compiler is making the faulty
assumption that T[] is an Object[] when in your case it isn't.
class Array extends java.lang.Object{
Array();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
static java.lang.Object[] create(java.lang.Class, int);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/
io/PrintStream;
3: aload_0
4: invokevirtual #3; //Method java/io/PrintStream.println:
(Ljava/lang/Object;)V
7: aload_0
8: iload_1
9: invokestatic #4; //Method java/lang/reflect/
Array.newInstance:(Ljava/lang/Class;I)Ljava/lang/Object;
12: checkcast #5; //class "[Ljava/lang/Object;"
15: checkcast #5; //class "[Ljava/lang/Object;"
18: areturn
}
Jerry
On 13 Dec 2006, at 15:20, Aeon B. C. Lee wrote:
Thanks. I know that Java Generics doesn't support primitives,
but that is a entirely different bug.
Please note that the following statement
byte[] b = (byte[])java.lang.reflect.Array.newInstance
(byte.class, 10);
is perfectly legal, because "The primitive Java types (boolean,
byte, char, short, int, long, float, and double), and the
keyword void are also represented as Class objects"
My code compiles without any problem, but gets a "
java.lang.ClassCastException: [B cannot be cast to
[Ljava.lang.Object" at runtime, which is just nonsense because
the cast is from array of byte to array of T (where T is byte).
Aeon
On Dec 13, 2006, at 9:10 AM, Jerry wrote:
On 13 Dec 2006, at 13:59, Aeon B. C. Lee wrote:
Can anyone tell me what's wrong with the last statement of my
code?
class Array
{
static <T> T[] create(Class<T> type, int length)
{
return (T[]) java.lang.reflect.Array.newInstance
(type, length);
}
}
public class NewMain
{
public static void main(String[] args)
{
byte[] b = (byte[])java.lang.reflect.Array.newInstance
(byte.class, 10); // This is OK
System.out.println(Array.create(Byte.class, 10)); //
So is this
System.out.println(Array.create (byte.class, 10)); //
WTF is wrong with this?
}
}
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4487555
Jerry
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