Re: Proposed new Java feature

Eric Sosman <esosman@ieee-dot-org.invalid>
Sun, 27 May 2012 17:51:57 -0400
On 5/27/2012 3:59 PM, Mike Schilling wrote:

"Eric Sosman"<esosman@ieee-dot-org.invalid> wrote in message

On 5/27/2012 3:04 PM, Mike Schilling wrote:

"Daniel Pitts"<> wrote in message

On 5/27/12 11:00 AM, Mike Schilling wrote:

"markspace"<-@.> wrote in message news:jptkmp$vbg$

On 5/26/2012 4:11 PM, Mike Schilling wrote:

Proposed feature: a static method on Thread that clears all
the current thread.

I can see your points. However, I don't have any real experience with
ThreadLocal, and when a neophyte agrees with your argument, that's a

Here's a blog where someone seems to have the same issue as you.


At the end of the comments, there's a suggestion to use
ThreadLocal::remove(), with the implication that it allows the thread
local variable to be garbage collection. Is there a reason that
work for you?

That acts on an individual ThreadLocal (and works quite well), but it
doens't allow removing all ThreadLocals that might have been

You're basically saying "This type of resource can leak if not cleared
appropriately, so there should be a 'Release all resources' method."

When paraphrased that way, does that make it clearer why it isn't a good
idea? It would be about the same as a "File.closeAll()" or a
"Socket.closeAll()" call. Extremely dangerous and only a crutch for not
doing the right thing to begin with.

Or a "collect all unused memory" call . Clearly, that's a crutch for not
keeping track of memory allocation properly in the first place. And the
fact that files and sockets are closed when a process exits is yet

     I'm with Daniel. Your code uses classes that you wrote, and
classes you got from somewhere else -- Sioux Unusuals, perhaps.
And if those classes use ThreadLocals for their own purposes, and
you blithely destroy them all, what happens then? Or what about
the class that invoked your code, passing an InheritableThreadLocal?
Is it a good idea to change parts of your invoker's state that you
don't understand, that you aren't even aware of?

Consider the use case again.

     I understood it fine the first time around, thanks. If you
think of anything new to add, pray do so.

[... reiteration of old material ...]

     I notice that you do not address any of the issues Daniel or I
raised; you just repeat what you "want." I know three-year-olds
who can do that, but I don't rush to grant their every whim.

Eric Sosman

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