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up vote 3 down vote favorite

So i am able to write: 

HashMap<String, ArrayList<Integer>> ...

but When it comes to a structure like 

HashMap<String, HashMap<Integer, ArrayList<Integer>>> ...

I fail...

Set<String> keys = outer.keySet();
List<String> list = sortList(keys);
Iterator<String> it = list.iterator();
HashMap<Integer,ArrayList<Integer>> inner=new HashMap<Integer,ArrayList<Integer>>();
                while (it.hasNext()) {
                    String key = it.next();
                    Set<Integer> ids= inner.keySet();
                    List<Integer> positions=sortList(ids);
                    Iterator<Integer> itIn=positions.iterator();
                    while(itIn.hasNext()){
                        String id= it.next();
                        output.write(key + "\t" + outer.get(key) + " " +inner.get(id) +"\n");
                    }
                }

My code can write all the keys outer has, and first elements of the Integer1 but can not see list or so on.
How can I make a connection with inner hashmap and outer hashmap?

share|improve this question
    
Are you sure you really meant to write this code? Look at the inner variable, you are instantiating it right now, and you want to iterate over it? That collection is empty, so there can't be no values inside it. –  SHiRKiT Jan 15 '12 at 14:56
    
I dont meant to, it is the best crude idea i had. yes, i could not figure out how to integrate the outer values to the inner –  anonym Jan 15 '12 at 15:04
    
Then stop thinking about hashmaps, arraylists and on, and start thinking as a matrix. What you have over there? A really special map. You map Srings into Integer and then into Integer again. So, thinking in a 3D matrix, we Have Matrix[String][Integer][Integer]. Try this approach if you can think up with a better solution. But this really looks like an error in the approach. Think as a 3D matrix and you'll get it. I've successfully made an idea to serialize a 3D Matrix, but while using your HashMap<String, HashMap<Integer, ArrayList<Integer>>> things got really complicated. –  SHiRKiT Jan 15 '12 at 15:16
1  
I'll give a try to that also –  anonym Jan 15 '12 at 15:19
    
Upvoted for you do your own try first. If you fail, please tell me again so I can show you a solution for this problem. –  SHiRKiT Jan 15 '12 at 15:21

2 Answers 2

up vote 3 down vote accepted

How about storing the whole object as a file via ObjectOutputStream? Something like:

public static void saveObject(HashMap<String, HashMap<Integer, ArrayList<Integer>>> obj, String filePath)
{
    OutputStream os = null;
    try
    {
        os = new ObjectOutputStream(new FileOutputStream(filePath));
        os.writeObject(obj);
    }
    catch(Exception ex){}
    finally
    {
        os.close();
    }
}

Then you can load it like:

public static HashMap<String, HashMap<Integer, ArrayList<Integer>>> loadObject(String filePath)
{
    HashMap<String, HashMap<Integer, ArrayList<Integer>>> obj = null;
    InputStream is = null;
    try
    {
        is = new ObjectInputStream(new FileInputStream(filePath));
        obj = (HashMap<String, HashMap<Integer, ArrayList<Integer>>>) is.readObject();
    }
    catch(Exception ex){}
    finally
    {
        is.close();
    }
    return obj;
}

Note that you need to implement the Serializable interface to use this object serialization.

share|improve this answer
up vote 0 down vote

Serialize the inner variable, it will take care of serializing all the references it holds inside.

As an aside note, why would you need such a nested data structure? it smells like a design problem.

share|improve this answer
    
I am storing, position indexes and file id's for each unique word within a big dataset. To do that, i thought this way would be nicer. –  anonym Jan 15 '12 at 15:09
    
But surely you could have simplified the design somehow, what you're creating is a maintainability headache –  Óscar López Jan 15 '12 at 15:11

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