Java Reference
In-Depth Information
cached number and factors. When a thread sets the volatile
cache
field to reference a new
OneValueCache
, the new cached data becomes immediately visible to other threads.
The cache-related operations cannot interfere with each other because
One-ValueCache
is immutable and the
cache
field is accessed only once in each of the relevant code paths.
This combination of an immutable holder object for multiple state variables related by
an invariant, and a volatile reference used to ensure its timely visibility, allows
Volat-
ileCachedFactorizer
to be thread-safe even though it does no explicit locking.
3.5. Safe Publication
So far we have focused on ensuring that an object
not
be published, such as when it is sup-
posed to be confined to a thread or within another object. Of course, sometimes we
do
want
to share objects across threads, and in this case we must do so safely. Unfortunately, simply
storing a reference to an object into a public field, as in
Listing 3.14
,
is
not
enough to publish
that object safely.
