On 18/11/14 15:14, Bernd Eckenfels wrote:
Am Tue, 18 Nov 2014 15:12:46 +0000
schrieb Chris Hegarty <chris.hega...@oracle.com>:
Interesting idea. If this was to be the case woultn't multiple get()
invocations cause multiple initialValue() invocations?
I think storing the null is important to obey the initialValue /
remove contract, i.e. initialValue method is invoked at most once per
thread, but it may be invoked again in case of subsequent invocations
of remove() followed by get().
Yes, either the contract has to change, or the empty
default implementation of initial value is changed to not return null
but INITIAL.
Yes, that was my initial thought too, but unfortunately initialValue
specifies that the default implementation returns null :-( So it would
require a specification change too, and it might be surprising to a
number of existing applications that rely on this default behavior.
-Chris.
final static protected Object INITIAL = new Object();
initialValue() { return INITIAL; }
...
if (value != INITIAL)
createMap();
This way a overwritten initialValue() is still called only after
remove() and only for a unaltered ThreadLocal the optimization applies.
Gruss
Bernd
