RFR: 8060130: Simplify the synchronization of defining and getting java.lang.Package

Mandy Chung mandy.chung at oracle.com
Sat Oct 11 20:29:31 UTC 2014

On 10/11/2014 8:17 AM, Remi Forax wrote:
> Hi Mandy,
> On 10/11/2014 02:31 AM, Mandy Chung wrote:
> [...]
>>> webrev: http://cr.openjdk.java.net/~redestad/8060130/webrev.02/
>> ClassLoader.java
>> line 272: can you change the declared type as Map.
> I think it's a bad idea, the class doesn't work if you replace the 
> ConcurrentHashMap by any Map
> so declaring the field 'packages' as a Map seems wrong to me.
> At least, it should be a ConcurrentMap, but even with a ConcurrentMap, 
> I think that the guarantee
> that in definePackage the call to putIfAbstent is amortized O(1) and 
> not something like O(ln n) is important.
> Note that using interfaces instead of implementations is important in 
> the signature of public or protected method, for a local variable or a 
> private field, which are hidden, there is no real reason to use an 
> interface. I understand that pedagogically having only one rule is 
> appealing but from my own experience, this rule hide one of the corner 
> stone of the OOP, encapsulation, so IMO the rule 'use an interface 
> everywhere you can' does more harm than good because it offers a 
> discorded version of the OO world.

Remi - thanks for catching this.  After I sent the comment, I was 
pondering my suggestion (this specific one) was a bad idea. Declaring it 
as Map loses the significance that the implementation depends on the 
packages map being concurrently accessed.   Agree.


More information about the core-libs-dev mailing list