JDK 9 pre-review of JDK-6850612: Deprecate Class.newInstance since it violates the checked exception language contract

joe darcy joe.darcy at oracle.com
Fri Apr 22 17:47:07 UTC 2016

Hi Roger,

Per other discussion in the thread, no new method will be introduced.

The area owners will need to cleanup this usage of this method since it 
may involve restructuring of catch blocks, etc., since the recommended 
approach has different exception behavior.



On 4/22/2016 8:33 AM, Roger Riggs wrote:
> Hi Joe,
> Wouldn't it be less make work to introduce the new method, replace the 
> current one where appropriate
> and then deprecate the existing method?  As it is, you/someone is 
> going to make a second pass
> over all the same files.
> Roger
> On 4/21/2016 12:25 PM, joe darcy wrote:
>> Hello,
>> After a generally positive reception, please review the webrev to 
>> implement the deprecation of Class.newInstance and the suppression of 
>> the resulting warnings:
>>     http://cr.openjdk.java.net/~darcy/6850612.0/
>> There are also some changes in the langtools repo; I'll send a 
>> separate review request for those changes to compiler-dev.
>> I'll also forward this review request to other areas with affected code.
>> Thanks,
>> -Joe
>> On 4/17/2016 10:31 AM, joe darcy wrote:
>>> Hello,
>>> With talk of deprecation in the air [1], I thought it would be a 
>>> fine time to examine one of the bugs on my list
>>>     JDK-6850612: Deprecate Class.newInstance since it violates the 
>>> checked exception language contract
>>> As the title of the bug implies, The Class.newInstance method 
>>> knowingly violates the checking exception contract. This has long 
>>> been documented in its specification:
>>>> Note that this method propagates any exception thrown by the 
>>>> nullary constructor, including a checked exception. Use of this 
>>>> method effectively bypasses the compile-time exception checking 
>>>> that would otherwise be performed by the compiler. The 
>>>> Constructor.newInstance method avoids this problem by wrapping any 
>>>> exception thrown by the constructor in a (checked) 
>>>> InvocationTargetException.
>>> Roughly, the fix would be to turn the text of this note into the 
>>> @deprecated text and to add a @Deprecated(since="9") annotation to 
>>> the method. There are a few dozen uses of the method in the JDK that 
>>> would have to be @SuppressWarning-ed or otherwise updated.
>>> Thoughts on the appropriateness of deprecating this method at this 
>>> time?
>>> Comments on the bug have suggested that besides deprecating the 
>>> method, a new method on Class could be introduced, 
>>> newInstanceWithProperExceptionBehavior, that had the same signature 
>>> but wrapped exceptions thrown by the constructor call in the same 
>>> way Constructor.newInstance does.
>>> Thanks,
>>> -Joe
>>> [1] 
>>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-April/040192.html

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