SAM interface/class figures [Re: Preparing for the 0.2 draft]

[Alex Buckley]

Thanks Alexey and Stephen. How are you producing these statistics?

Alexey, do you really mean 1920 SAM *classes*, or 1920 SAM types? 
Because if 7474 anon.classes extend a class, and 12597 anon.classes 
extend a "SAM", then some of those "SAM" things must be interfaces. What 
is really interesting is how many of those 12597 anon.classes extend a 
SAM class v. implement a SAM interface.

Alex

Alexey Kudravtsev wrote:
> These are figures for the Intellij IDEA (http://www.jetbrains.com/idea/) 
> source base.
> 
> Total files inspected: 34794
> Total java classes: 69703
> All SAM classes: 1920 (2,8%)
> All Anonymous classes: 21908 (31,4%)
>   anonymous classes which Extend class: 7474 (34,1%)
>   anonymous classes which implement interface: 14434 (65,9%)
> 
>   anonymous classes which extend SAM: 12597 (57,5%)
> 
>   anon classes with single method: 18431 (84,1%)
>   anon classes with fields: 149 (0,7%)
>   anon classes with 'this' references: 116 (0,5%)
>   anon classes with qualified 'this' references: 77 (0,4%)
>   anon classes which recurse: 15 (0,1%)
> 
> Alexey Kudravtsev
> Intellij IDEA developer
> JetBrains, Inc
> http://www.jetbrains.com
> "Develop with pleasure!"
> 
>> Message: 1
>> Date: Fri, 29 Jan 2010 00:56:46 -0800
>> From: Alex Buckley <Alex.Buckley at Sun.COM>
>> Subject: Preparing for the 0.2 draft
>> To: "lambda-dev at openjdk.java.net" <lambda-dev at openjdk.java.net>
>> Message-ID: <4B62A2CE.7080300 at sun.com>
>> Content-Type: text/plain; CHARSET=US-ASCII; format=flowed
>>
>> Many thanks for everyone's comments on the 0.1 draft. The "foo.()"
>> invocation syntax looks like a winner, and I am seriously considering
>> rearranging the function type syntax to have argument types first.
>> Requiring a lambda expression to denote its return type is also
>> increasingly appealing. SAM classes are staying for now.
>>
>> The discussion of transparent 'this' v. non-transparent 'this' comes
>> down to the question of what a lambda in Java is for. (Zdenek Tronicek
>> ably made this point earlier.) Part of the answer lies in understanding
>> when to use an anonymous inner class and when to use a lambda
>> expression. A step towards that understanding would be knowing how
>> anonymous inner classes are used today.
>>
>> It would be very interesting if list members could provide the following
>> statistics for codebases with which they are familiar:
>>
>> - What %age of anonymous inner classes declare a single non-Object method?
>> - What %age of single-method anonymous inner classes declare fields?
>> - What %age of single methods in anonymous inner classes use 'this'?
>> - What %age of single methods in anonymous inner classes recurse?
>> - Are the %ages different for anonymous inner classes that implement an
>> interface v. that extend a class ?
>>
>> (As well as anonymous inner classes, any utility class that
>> implements/extends a SAM type is of interest, such as this nested class
>> from the extra166y.ParallelArray Javadoc:
>>   static final class IsSenior implements Predicate<Student> {
>>      public boolean op(Student s) { return s.credits > 90; }
>>    }
>> )
>>
>> Alex
>>
> 
>