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NNTP-Posting-Date: Sun, 16 Oct 2011 19:02:43 -0500
Date: Mon, 17 Oct 2011 01:02:44 +0100
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: constructing a constant HashMap
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Tom Anderson wrote:
> On Sun, 16 Oct 2011, B1ll Gat3s wrote:
> 
>> On 16/10/2011 1:07 AM, Patricia Shanahan wrote:
>>> Roedy Green wrote:
>>>> What is your preferred way of building a HashMap when all the values
>>>> are known at compile time?
>>>
>>> If the map is a field, I often use an instance or static initializer
>>> immediately after the map's declaration:
>>>
>>> Map<String,String> myMap = new HashMap<String,String>();
>>> {
>>> myMap.put("aaa", "bbb");
>>> ...
>>> }
> 
> For static final variables (suggested by "all the values are known at 
> compile time"), i would suggest a slight variation:
> 
> static final Map<String,String> myMap;
> static {
>     Map<String,String> tmpMap = new HashMap<String,String>();
>     tmpMap.put("aaa", "bbb");
>     myMap = Collections.unmodifiableMap(tmpMap);
> }

Yes, that is indeed an improvement, given the lack of intent to modify
the map after its creation.

Patricia