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static maps

Posted on 2012-03-14
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Last Modified: 2012-03-24
How do I implement a static map class to be used by a few other classes?
examples to follow will be great.
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Question by:dpalyca755
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2 Comments
 
LVL 47

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by:for_yan
ID: 37721968
can you please elaborate?

HashMap as any Java object can be made static and then you could address it by refereinng to the class name rather than the instance of the class where it is a field
So if you declare it like that:
class ClassName {
public static HashMap<Integer, String> map;
...


}

Thane in any other class of your applucation you can address it like that:

ClassName.map.get(key)

thsi is no different form any other static object
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gudii9 earned 2000 total points
ID: 37722491
Here is interesting explanation, links

public static Map CONSTANTS = new HashMap() { {
put("key1", "value1");
put("key2", "value2");
}};


Even better is to wrap the ArrayList/HashMap by passing them to Collections.unmodifiableList or Collections.unmodifiableMap. Thus making sure that it is truly a constant list/map.

http://livinginjava.blogspot.com/2010/08/initialize-static-list-and-map.html
http://stackoverflow.com/questions/507602/how-to-initialise-a-static-map-in-java
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