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

From	Alex J <vstrength@gmail.com>
Newsgroups	comp.lang.java.machine
Subject	Why "lock" functionality is introduced for all the objects?
Date	2011-06-28 02:30 -0700
Organization	http://groups.google.com
Message-ID	<736a142e-85ae-4790-a1f1-afb09bfed755@em7g2000vbb.googlegroups.com> (permalink)

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I'm curious why Java designers once decided to allow every object to
be lockable (i.e. allow using lock on those).
I know, that out of such a design decision every Java object contain
lock index, i.e. new Object() results in allocation of at least 8
bytes where 4 bytes is object index and 4 bytes is lock index on 32-
bit JVM.
I think that it just inefficient waste of space, because not all the
objects requires to be lockable/waitable.

The better decision, IMHO, would be to introduce lock/wait mechanics
for only, say, the Lockable descendants.
The current approach seems to be very simple, but is the performance
penalty so small for not be taken into an account?
Eclipse uses tons of small objects and I guess that is why it consumes
so much memory while a significant part of it is never used.

What do you think of it?

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Thread

Why "lock" functionality is introduced for all the objects? Alex J <vstrength@gmail.com> - 2011-06-28 02:30 -0700
  Re: Why "lock" functionality is introduced for all the objects? Roedy Green <see_website@mindprod.com.invalid> - 2011-06-28 10:02 -0700
  Re: Why "lock" functionality is introduced for all the objects? Barb Knox <see@sig.below> - 2011-06-30 18:11 +1200

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