Re: Why "lock" functionality is introduced for all the objects?

Robert Klemme <>
Wed, 29 Jun 2011 18:56:43 +0200
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:


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.


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.


Kind regards


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