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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: Why "lock" functionality is introduced for all the objects?
Date: Wed, 29 Jun 2011 18:56:43 +0200
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On 28.06.2011 19:53, Michal Kleczek wrote:
> Lew wrote:
>
>> On 06/28/2011 12:41 PM, Michal Kleczek wrote:
>>> Lew wrote:
>>>
>>>> Alex J wrote:

<snip/>

> Yet in the end the community seems to agree not to use "synchronized"
> directly but rather use classes from java.util.concurrent (namely Lock and
> Condition). So is this keyword really that important?

Where do you take that from?  I know at least two cases from my recent 
development history where it came in extremely handy that all objects 
have a monitor.  In those cases where there were a lot of objects stored 
and we needed to synchronize on each individual object to prevent a 
bottleneck and allow scalability a solution using an implementation of 
java.util.concurrent.locks.Lock almost certainly would have used 
significantly more memory.

<snip/>

>> Show me the numbers.  What penalty?
>
> It is (almost) twice as much memory as it could be and twice as much GC
> cycles. Almost because in real world the number of objects that you need to
> synchronize on is way lower than the number of all objects you create.

I'd say that heavily depends on the application type.  I don't think 
such a general statement is warranted.

<snip/>

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/