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Array of ArrayLists

 
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I have an array of arrayLists:
Focus on public ArrayList[] nodeInfo = new ArrayList[100];




Result:
[0, qw, 200, 20, 109, 647, 499]
[1, az, 350, 50, 133, 260, 259]
array of arraylist null
array of arraylist null


WHAT IS WRONG WITH MY CODE???
I WANT a array with individual elements storing an arraylist and which can be accessed within any other method.
please help!!!
 
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When you do this:


What do you think nodeInfo[i] is giving you?

Hunter
 
Rose Jac
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i think nodeInfo[i] will give me the nodeList saved at this ith index.
Am i wrong?
 
Hunter McMillen
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Right, so how can you access individual elements of a nodeList(i.e ArrayList)
 
Rose Jac
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But i need the individual elements of the Array i.e.every ArrayList stored in the Array as its elements and not the individual elements of the ArrayList.
Also, the elements of the Array are coming as null, so i guess, the individual elements of the ArrayList would also come as null, isnt it?
 
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Rose Jac wrote:
Also, the elements of the Array are coming as null, so i guess, the individual elements of the ArrayList would also come as null, isnt it?



When the elements of Array are coming as null, that means there are no ArrayList objects, at that index.

Then why do you even think of individual elements of ArrayList.. ?
 
Rose Jac
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Thats what i said.
Any help on how i can actually do that?
Thanks!
 
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Hi, Rose Jac,

It would be better to change the code to not use an "array of ArrayList". An array of ArrayList ( or any collection within another collection ) makes the code difficult to read and maintain. Instead an ArrayList of POJOs would be more readable and maintainable.

It would look something like this :



This is called a "Data Transfer Object"


Now, you can retrieve from database like this

 
Rose Jac
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hI Vishwanath Krishnamurthi,

That sounds fairly simple though before implementing it, what i would like to know is : say, i have n number of records in the database, then would i be able to access all these records at once using DTO?

Thanks!
 
Vishwanath Krishnamurthi
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Sorry, I don't understand your question clearly. Typically you'd iterate through the recordset, create one DTO object corresponding to one row retrieved, and add that DTO to the ArrayList.
So If you have 100 rows retrieved by a query, then you'd have an ArrayList that contains 100 DTOs.

HTH,
Vishwa
 
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