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From: Lew <lewbloch@gmail.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: Substitute value in HashMap at runtime
Date: Thu, 13 Oct 2011 10:12:46 -0700 (PDT)
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Robert Klemme wrote:
> mike wrote:
>> If I create a HashMap with something like:
>>
>> static Map<String,String> map = new
>> HashMap<String,String>("variable",MyPreferences.getVariableValue());
>>
>> If I do it like this I guess that MyPreferences.getVariableValue()
>> will not be substituted but be the "plain" string.
>>
>> How can I make my MyPreferences.getVariableValue() be evaluated at
>> runtime? Any example?
> 
> One possible way is to change your Map to Map<String,
> Callable<String>> and invoke call() at runtime.
> 
> http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Callable.html
> 
> Of course you then need to provide a proper implementation. :-)
> 
> Btw, does your Map contain more entries?  If not, it's completely
> superfluous.
> 
> If you define the Map as static you also need to be aware of
> concurrency issues if your application will ever access this from
> multiple threads.

It doesn't even have to be multiple threads.  Multiple instances in the same thread can clobber a static structure if careless.  They just take turns messing each other up.

-- 
Lew