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Why doesn't my hashtable populate? Java

Posted on 2012-03-20
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Last Modified: 2012-03-20
I'm trying to pre-populate a Hashtable from a different class called ZipCodes

Here's my ZipCodes class with some test data:

import java.util.Hashtable;

public class ZipCodes {
	final static Hashtable<String, String> zipCodesList
    = new Hashtable<String, String>();
	public static void main() {

		zipCodesList.put("00501", "NY218");
		zipCodesList.put("00544", "NY218");
		zipCodesList.put("00601", "XX499");
		zipCodesList.put("31036", "GA076");
		zipCodesList.put("31037", "ZZ560");
		zipCodesList.put("31038", "ZZ740");
	        return;
	}

}

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When I call upon ZipCodes in my code, it compiles fine, it just doesn't have data inside of it.

Here's what my call looks like:

Hashtable<String, String> zipCodesListing = ZipCodes.zipCodesList;
    	      cityName = zipCodesListing.get(cityCode);

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The actual part where it does a .get(cityCode) works when the hashtable is being declared and populated in my main code.  But all it's returning is null.
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Question by:Dale Harris
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7 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 37745368
Show how two pieces of your code actuall are comabined. when you execute the second snippet ?
0
 
LVL 16

Author Comment

by:Dale Harris
ID: 37745371
Yes.  It's based on a button push.  The class that I posted called ZipCodes is a standalone class in it's entirety.  That's all it does.  All the rest of my code is in my main java file.
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LVL 47

Expert Comment

by:for_yan
ID: 37745372
This part will just execute, ppulate Hashatble and then exit

public static void main() {

		zipCodesList.put("00501", "NY218");
		zipCodesList.put("00544", "NY218");
		zipCodesList.put("00601", "XX499");
		zipCodesList.put("31036", "GA076");
		zipCodesList.put("31037", "ZZ560");
		zipCodesList.put("31038", "ZZ740");
	        return;
	}

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- so when would you have a chance to say this:

Hashtable<String, String> zipCodesListing = ZipCodes.zipCodesList;
                cityName = zipCodesListing.get(cityCode);
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LVL 47

Expert Comment

by:for_yan
ID: 37745375
No you can't do that - this class will execute and go away together with your Hashtable


You shuld do something like that - all from when you push the button
ZipCodes.populate();
Hashtable<String, String> zipCodesListing = ZipCodes.zipCodesList;
                cityName = zipCodesListing.get(cityCode);




public static void populate() {

		zipCodesList.put("00501", "NY218");
		zipCodesList.put("00544", "NY218");
		zipCodesList.put("00601", "XX499");
		zipCodesList.put("31036", "GA076");
		zipCodesList.put("31037", "ZZ560");
		zipCodesList.put("31038", "ZZ740");
	        
	}

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0
 
LVL 47

Accepted Solution

by:
for_yan earned 2000 total points
ID: 37745378
That should ber your class:

import java.util.Hashtable;

public class ZipCodes {
	final static Hashtable<String, String> zipCodesList
    = new Hashtable<String, String>();
	public static void populate() {

		zipCodesList.put("00501", "NY218");
		zipCodesList.put("00544", "NY218");
		zipCodesList.put("00601", "XX499");
		zipCodesList.put("31036", "GA076");
		zipCodesList.put("31037", "ZZ560");
		zipCodesList.put("31038", "ZZ740");
	        
	}

}
                                  

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and thats how it acn be used in another class:

ZipCodes.populate();
Hashtable<String, String> zipCodesListing = ZipCodes.zipCodesList;
                cityName = zipCodesListing.get(cityCode);

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0
 
LVL 16

Author Comment

by:Dale Harris
ID: 37745387
That was it!  Thanks.  Now I understand what you mean.  It's creating the variable because it's above the method.  But it wasn't doing the rest of it because it was not being called.

Thanks again!
0
 
LVL 16

Author Closing Comment

by:Dale Harris
ID: 37745388
Great, fast, easy solution!
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