Android: Create List<Map<String, List<ObjectType>>

Question

Can someone help me solve my problem, how to create List<Map<Integer, List<MyType>> in while cycle. I'm selecting data from database and I'd like to add objects, that accomplish select's where condition into List and then put it into Map<Integer, List<MyType> where map key is in my case integer from database column order_num. Finally I would like to add all created maps into List. Method's return value is List<Map<Integer, List<MyType>>>.

Here's my part of source:

while (cursor.moveToNext) {
       int id = cursor.getInt(cursor.getColumnIndex("item_id"));
       int orderNum = cursor.getInt(cursor.getColumnIndex("order_num"));
       String name = cursor.getString(cursor.getColumnIndex("item_name"));

       list.add(new Item(id, orderNum, name);
   }

now I'd like to add this list into Map where key is orderNum and value is List<Item>.

Khantahr · Accepted Answer · 2013-01-02 19:54:37Z

2

I'd declare an orderNum variable outside the loop so you can use it when the loop finishes:

int orderNum;
for ( cursor.moveToFirst; !cursor.isAfterLast(); cursor.moveToNext )
{
    int id = cursor.getInt( cursor.getColumnIndex( "item_id" ) );
    orderNum = cursor.getInt( cursor.getColumnIndex( "order_num" ) );
    String name = cursor.getString( cursor.getColumnIndex( "item_name" ) );

    list.add( new Item( id, orderNum, name ) );
}

map.put( orderNum, list );

I guess that whole block will be in some sort of loop too, so when that loop finishes then you can do

masterList.add( map );

answered Jan 2, 2013 at 19:54

Khantahr

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3 Comments

codeMagic Over a year ago

Wouldn't you want to add to the map inside the loop? Otherwise you are only adding one data set to the map instead of each row from DB. Or did I misunderstand the question?

Khantahr Over a year ago

As I understood the question, the loop he has creates a list of data sets from the database query, then he wants to add that list to a map, each entry of which corresponds to one of his queries.

codeMagic Over a year ago

+1 for probably being right :) I wasn't sure which way the OP was wanting to do it so I made the suggestion just in case

Jasper Fioole · Accepted Answer · 2013-01-02 19:54:37Z

0

Ty using a hashmap instead. I'm not sure if this work, but you can at least try it.

HashMap<Integer, ArrayList<MyClass>> myMap = new HashMap<Integer, ArrayList<MyClass>>();

Maybe this helps as well: http://www.roseindia.net/javatutorials/javahashmap.shtml

answered Jan 2, 2013 at 19:54

Jasper Fioole

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