RFR: JDK-5108778 Too many instances of java.lang.Boolean created in Java application

[Stuart Marks]

On 10/6/15 6:06 AM, Alexander Scherbatiy wrote:
> On 10/3/2015 5:40 AM, Stuart Marks wrote:
>> The weird one is in AquaTabbedPaneUI.java, which has
>>
>>     protected Boolean isDefaultFocusReceiver = null;
>>
>
>    I do not mean to change the isDefaultFocusReceivertype type to boolean. It
> was just interesting are there pros and cons to use a short version with
> autoboxing  for assignment:
>        isDefaultFocusReceiver = defaultFocusReceiver != null &&
> defaultFocusReceiver.equals(component);
>    instead of the long version:
>        isDefaultFocusReceiver = Boolean.valueOf(defaultFocusReceiver != null &&
> defaultFocusReceiver.equals(component));

I agree, changing Boolean to boolean here is too invasive for a cleanup change.

Right, the "interesting" issue is if this code were changed to use autoboxing, 
it would end up being this:

     if (isDefaultFocusReceiver == null) {
         // ...
         isDefaultFocusReceiver = defaultFocusReceiver != null && 
defaultFocusReceiver.equals(component);
     }

The isDefaultFocusReceiver field is being checked against null and then a 
boolean value is being assigned to it. That looks strange.

I guess in this case the call to Boolean.valueOf() makes it clearer what's going 
on. But I'll leave the final decision to you.

s'marks

>
>     Thanks,
>     Alexandr.
>
>> Ugh! It would be nice to get rid of null as a marker for uninitialized state,
>> but that might require too much analysis to show that the change would be
>> correct. This is, I think, the only case where the code has to be explicit
>> about dealing with a boxed Boolean object that might be null, as opposed to
>> true or false.
>>
>> The only place that really has to do that is isDefaultFocusReceiver(), which
>> checks for null up front. I'm not sure that using Boolean.valueOf() and
>> Boolean.booleanValue() in the rest of the method are really helpful in
>> denoting that this is a boxed, nullable Boolean though. So I'd switch to
>> autoboxing here too.
>>
>> s'marks
>