why isn't oop's modularity thread-safe?

8.6: adda/concurrency/oop`modular not threadsafe:

. assuming the oop lang's were very modular;
why wouldn't they be easy to distribute?
some have said it's the central heap model .
. in fact,
java was not really that modular:
whether it was from obj' vs value semantics
or letting other objects share in the
modification of locals,
or simply not being able to
finish one self change
before being read by another thread,
java was not always threadsafe .
. to be {concurrently modular, threadsafe},
class methods need to be atomic
as are Ada's protected types .

. would it help if they didn't share?
[8.17: ie,
why is the default assignment a pointer share;
or, why have sharing pointers without
distinguishing sharers from owners ? ]

[8.17: can't we find concurrency elsewhere?]
. the basic structure hasn't changed
(programs = dstrs + algor's):
obj`methods are serving up only brief procedures;
the bulk of processing comes from the
algorithm that employees the obj's .
[8.17: no:
. even if the methods are brief,
and even if there are many subroutine calls;
all the leaf calls are to obj`methods
-- and most time is actually spent in leaf calls;
at the algorithm level,
we can identify many concurrable calls
for which the compiler can verify
that what we are calling concurrent
in fact involves no object var'sharing .]