Dear Module owners and Developers,
For removing the excessive use of these objects using "new Boolean(),
new Integer(), new Byte() .. " we are experimenting the NetBeans Jackpot
Transformation tool :
http://jackpot.netbeans.org/ to replace code as
below to use the objects from Cache.
// Effective Java, Item 4: Avoid creating duplicate objects
new java.lang.Boolean($b) => java.lang.Boolean.valueOf($b);
new java.lang.Byte($b) => java.lang.Byte.valueOf($b);
new java.lang.Character($c) => java.lang.Character.valueOf($c);
new java.lang.Integer($i) => java.lang.Integer.valueOf($i);
new java.lang.Long($l) => java.lang.Long.valueOf($l);
new java.lang.Short($s) => java.lang.Short.valueOf($s);
new java.lang.String($s) => $s :: $s instanceof java.lang.String;
You can refer to the email thread for more details. Jan and myself tried
this on appserv-jstl and appserv-commons modules, and I could find
following diffs where this transformation matches and replaces in
appserv-commons module.
http://glassfishbuildtools.sun.com:8000/jackpot_acommons.log
We will be running this transformation on all the modules, so if you
have any comments, suggestions or if you prefer to do it yourself on
your own modules please let me know.
thanks
Dinesh
> Hi Tom,
> Tom Ball wrote On 10/17/06 14:04,:
>
>> Charlie is right: these sorts of transformations are trivial and
>> safe for Jackpot to do. Here are the relevant rules:
>>
>> // Effective Java, Item 4: Avoid creating duplicate objects
>> new java.lang.Boolean($b) => java.lang.Boolean.valueOf($b);
>> new java.lang.Byte($b) => java.lang.Byte.valueOf($b);
>> new java.lang.Character($c) => java.lang.Character.valueOf($c);
>> new java.lang.Integer($i) => java.lang.Integer.valueOf($i);
>> new java.lang.Long($l) => java.lang.Long.valueOf($l);
>> new java.lang.Short($s) => java.lang.Short.valueOf($s);
>> new java.lang.String($s) => $s :: $s instanceof java.lang.String;
>>
>> Float and Double constructors aren't changed because their valueOf
>> implementations don't currently have caches, but they can be both for
>> source consistency and to potentially take advantage of future
>> runtime performance enhancements. I'd be happy to run this over your
>> source base if you like, or you can install Jackpot in your NetBeans
>> IDE (http://jackpot.netbeans.org), open the Refactoring Manager,
>> create a new rule file, and paste in the above.
>
> works like a charm!
> Jan
>
>> Speaking of performance enhancements, I don't recommend spending time
>> trying to micro-optimize the new code. Regardless of whether one can
>> write a more efficient valueOf implementation than the core team,
>> HotSpot is going to optimize it for you if it becomes a problem. The
>> best way to ensure that HotSpot can optimize it is to write clear,
>> standard code which it can easily recognize.
>> Tom
>> Charlie.Hunt_at_Sun.COM wrote:
>>
>>> Why not write a Jackpot transformation to do all this code
>>> re-engineering for you?
>>> Jackpot could scan the entire GlassFish source in a matter of
>>> seconds and do the entire transformation in one click. You just
>>> need to write a line or two of transformation code to recognize the
>>> pattern and what you want to replace it with.
>>> If you talk with Tom Ball, cc'd here, I'm he would likely help get
>>> someone started.
>>> This Boolean and Integer transformation would be great candidates to
>>> add the Jackpot transformation repository for NetBeans.
>>> See http://jackpot.netbeans.org for more information on Jackpot.
>>> charlie ...
>>> Kin-man Chung wrote:
>>>
>>>> I have seen codes like new String("blah")! :-)
>>>> Wonder why javac not just silently turn "new Boolean(true)" into
>>>> Boolean.TRUE and "new Boolean(x)" into "x? Boolean.TRUE:
>>>> Boolean.FALSE"?
>>>> Also wonder if "x? Boolean.TRUE: Boolean.FALSE" may not be more
>>>> efficient than Boolean.valueOf(x)?
>>>> -Kin-man
>>>> On Fri, 2006-10-13 at 17:13, Craig L Russell wrote:
>>>>
>>>>> Note that valueOf(boolean) was introduced in JDK 1.4, and many of
>>>>> these are left over from previous releases.
>>>>> +1 to replacing the new Boolean with valueOf.
>>>>> Craig
>>>>> On Oct 13, 2006, at 5:03 PM, Jan Luehe wrote:
>>>>>
>>>>>> I've monitored the number of java.lang.Boolean instances on the heap
>>>>>> after different types of operations using 9.1 b21.
>>>>>>
>>>>>> After starting, I see approx. 1,300 instances, occupying
>>>>>> approx. 21,000 bytes. Each deploy of a very simple webapp adds
>>>>>> another 1,200 instances, and each undeploy adds 500.
>>>>>>
>>>>>> All of these instances will be gc'ed eventually, but at any time
>>>>>> during the appserver lifecycle, there should be no more than
>>>>>> 2 instances of java.lang.Boolean (Boolean.TRUE and Boolean.FALSE)
>>>>>> on the heap.
>>>>>>
>>>>>> If you search the GlassFish code base, you'll find tons of places
>>>>>> where "new Boolean(x)" instead of the recommended
>>>>>> "Boolean.valueOf(x)"
>>>>>> is used. I've also seen places where "new Boolean(true)" or
>>>>>> "new Boolean("true")" is used instead of Boolean.TRUE.
>>>>>>
>>>>>> All of this is flagged by FindBugs (along with "new Integer(x)" vs
>>>>>> "Integer.valueOf(x)", etc.).
>>>>>>
>>>>>> Fixing this is a very low-hanging fruit. We've already cleaned up
>>>>>> most of the web code.
>>>>>>
>>>>>> Jan
>>>>>