RFR 7118066: Warnings in java.util.concurrent package

[Maurizio Cimadamore]

On 06/12/11 08:01, Rémi Forax wrote:
> On 12/06/2011 08:07 AM, David Holmes wrote:
>> On 6/12/2011 12:14 PM, David Holmes wrote:
>>> On 6/12/2011 11:45 AM, Rémi Forax wrote:
>>>> On 12/06/2011 02:12 AM, David Holmes wrote:
>>>>> Is the reason for constructs like this:
>>>>>
>>>>> HashEntry<K,V>[] tab = (HashEntry<K,V>[])new HashEntry<?,?>[cap];
>>>>>
>>>>> that we can't utilize diamond? Otherwise it would nicely reduce to:
>>>>>
>>>>> HashEntry<K,V>[] tab = new HashEntry<>[cap];
>>>>
>>>> This should not compile because otherwise you can write
>>>
>>> This compiles fine:
>>>
>>> @SuppressWarnings("unchecked")
>>> public class TestGenerics<K,V> {
>>>
>>> static class HashEntry<K,V> { }
>>>
>>> public void m() {
>>> HashEntry<K,V>[] newTable = new HashEntry<>[1];
>>> }
>>> }
>>>
>>>
>>> I don't know exactly what the type inference code does but I assumed it
>>> effectively converted the above to:
>>>
>>> HashEntry<K,V>[] newTable = (HashEntry<K,V>[]) new HashEntry[1];
>>>
>>> and not to:
>>>
>>> HashEntry<K,V>[] newTable = new HashEntry<K,V>[1];
>>>
>>> which of course does not compile.
>>
>> Hmmm. Perhaps this is a compilation accident? I don't see anything in 
>> the spec that allows diamond to be used with array creation expressions.
>
> Yes, it's a bug of javac, eclipse compiler rejects this code.
Was a bug [1] ;-) - if you compile with a recent JDK 8 compiler, you get 
the following:

TestBug.java:12: error: cannot create array with '<>'
   HashEntry<K,V>[] newTable = new HashEntry<>[1];
1 error

[1] - http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7057297

Maurizio
>
>>
>> David
>> -----
>
> Rémi
>