List to Map

Hi
I have code:
Map a = new HashMap();
        for(int k=0;k<lis.size();k++){
         a.put(lis.get(k)[0], lis.get(k)[1]);
         System.out.println("L:"+lis.get(k)[0]+"\nm:"+a);
        }and lis is
ArrayList<Object[]> lis = new ArrayList();out is:
L:siedziba
m:{siedziba=qq}
L:data
m:{data=2008-04-03, siedziba=qq}
L:regon
m:{regon=123456789, data=2008-04-03, siedziba=qq}
L:ekd
m:{ekd=7411, regon=123456789, data=2008-04-03, siedziba=qq}
L:nipp
m:{ekd=7411, regon=123456789, data=2008-04-03, nipp=, siedziba=qq}
L:peselp
m:{ekd=7411, peselp=, regon=123456789, data=2008-04-03, nipp=, siedziba=qq}
How put Object to Map that new Object insert on last position on Map ??
(example:
wrong:
m:{ekd=7411, peselp=, regon=123456789, data=2008-04-03, nipp=, siedziba=qq}
correctly:
m:{ siedziba=qq, data=2008-04-03, regon=123456789,ekd=7411, nipp=, peselp=}
Or how to set Set.iterator to get value Object from Map in the same order as in List ??
PS.
Sorry for my bad english :)

LRMK wrote:
Order of objects in the map depends on its implementation. Hash map does not have make any promises on order. To my understanding there is no map implementation that keep the insertion order in tact. So you cant do this unless you implement something on your ownLinkedHashMap does

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Hi there!:
I've been checking this forum for information about something like what I state in the title of this message, but haven't found such a specific case. I'm commenting my doubt below.
I'm working with a list of maps whose keys are exactly the same in all them (they're of type String). Indeed it could be considered an extrapolation of a database table: The list contains maps which act as rows, and every map contains keys and values which represent column names and values.
However, this means to repeat the same key values on every map and this spends memory. Right, maybe it's not such a big spent, but since the list can contains thousands of maps, I think that it would be better to choose a more "economical" way to achieve the same result.
I had thought about building a class which stored everything as a list of lists and, internally, it mapped that String keys with the corresponding Integer indexes of every list. But then I realized that maybe I was re-inventing the wheel, because it's very probable that someone has already made that. Maybe is there a class on the Core API which allows that?
Thank you very much for your help.

Well, after re-reading the Java tutorial which is located in the Sun website I've came to a conclusion which I should have before, when I thought about using StringBuffers as keys of the maps instead of Strings.
I'm so used to build Strings using literals instead of the "new String ()" constructor (just as everyone) that I had forgotten that, as it happens with any kind of object but not the primary data types, Strings are not passed to the methods by value, but by reference. The fact of them being immutable made me think that they were passed by value.
Apart of that, my problem also was that using literals I was creating different String objects every time, despite the fact that they were equal about their content (making 400 different keys called "name" for example)
In other words, I was doing something like this:
// It makes a list of maps which will contain maps of boy's personal data (as if they were "rows" in a table).
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// It loops over a list of Boy objects, obtained using EJB.
for (Boy boy : listBoy) {
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}Well, the "problem" here (being too demanding, but I'm :P ) is that I was adding all the time new Strings objects as keys in every map. The key "name" in the first map was different from "name" in the second one and so on.
I guess that my knowledge got messed at certain point and thought that it was impossible to use exactly the same String object in different maps (the reference, not the same value!). Thus, my idea of using StringBuffers instead.
But thinking about it carefully, Why not to do this?:
List <Map <String, Object>> listData = new ArrayList <Map <String, Object>> (listBoy.size ());
// It makes the necessary String keys previously, instead of using literals on every loop later.
String name = "name";
String surname = "surname";
for (Boy boy : listBoy) {
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     Map <String, Object> map = new HashMap <String, Object> (2);
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I guess that using "javap" and disassembling the generated bytecode is the only way to make sure that it's that way.
I believe that it's solved now :) (if no one tells me the contrary). I still am mad at myself for thinking that Strings were passed by value. Thinking about it now it had no sense!
dannyyates: It's curious because re-reading every answer I think that you maybe were pointing to this solution already. But the sentence "you put the +same+ string" was a little ambiguous for me and thought that you meant putting the same String as "putting the same text" (which I already was doing), not the same object reference (in other words, using a common variable). I wish we could have continued discussing that in depth. Thanks a lot for your help anyway :) .

Sorting in List Hash Map

Hi All ,
I i have the data in below format:
Name     Age     Skill     Company
Vass     21     Java     Zylog
Samy     24     PB     HP
Lee     18     ADF     CTS
Reng     16     Java     Info
I converted this data into java collections List<Hash Map> like this.
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
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List<HashMap> is type of collection is help to me?
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Check out Comparator, and use Google to find examples on how to use it.
http://download.oracle.com/javase/6/docs/api/java/util/Comparator.html
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Hi friends,
I have a small problem. I want to iterate through a list of items, using struts.
The list actually contains map structres for example:
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list(1)
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HI,
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� map.get(attribute) == genObj.attribute
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IC.

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Please do not double post the threads, i answer this in your first thread, thanks
If I help you with any inquire, thank you for click kudos in my post.
If your issue has been solved, please mark the post was solved.

List to Map

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