On 7/9/18 11:59 PM, Peter Levart wrote:
There are situations where being able to create a XxxReference without a
referent is useful. For example, imagine a doubly-linked list of
WeakReference subclasses - a special instance without a referent can be
used as the head of such list that never goes away and simplifies
insertion/deletion logic, etc...
JDK's java.lang.ref.Cleaner API uses such scheme in its implementation
(see jdk.internal.ref.CleanerImpl.[Phantom|Weak|Soft]CleanableRef no-arg
constructors).
Thanks for pointing this out. It's used as a convenience and it's
not hard to handle insertion/deletion logic though. Another
alternative may be to create an object as the strongly reachable
referent. I wonder if any existing code depends on null referent
like the cleaner case and the compatibility risk. Do you know
any other example?
Mandy
