Nico wrote:
> Bob Hanson wrote:
>> pps. The following is more elegant and also works:
>>
>> static Boolean[] testInit = new Boolean[1];
>> private void initialize() {
>> if (testInit[0] != null) {
[snip]
>> It takes advantage of the fact that static testInit[0] has THREE
>> possible values: null, false, and true.
>> This is what I'm going with for now.
>>
>
> That won't work in every situation :
> - thread 1 executes "if (testInit[0] != null)" and finds that it evals
> to false
> - thread 2 executes "if (testInit[1] != null)" and finds that it evals
> to false also
> - thread 1 goes on
> - thread 2 goes on
>
> You could try using a synchronization on a variable.
Nico is correct.
It is not possible to "roll your own" synchronization in a high level
language without having some type of atomic 'test-and-set' operation
support at a lower level.
Essentially all CPUs for the last 50 years have had this, but popular
high-level languages have not exposed this functionality. Java is arguably
the first commercially-successful-and-broadly-accepted language that
incorporates synchronization primitives into the language.
Per Nico's other message, my bug with 'initialize' is that it was marked
'synchronized' instead of 'syncronized static'.
Miguel
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