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List to Map

Posted on 2014-10-23
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Last Modified: 2014-10-24
hi experts

In my database table i have data like this

Product                 type              currency

IMAGE-CARTS        SamInc.               USD
IMAGE-CARTS        BCI                   USD
IMAGE-CARTS        RII                        USD
IMAGE-CARTS        POP                  USD

POP-CARTS        SamInc.               USD
POP-CARTS        BCI                         USD
POP-CARTS        RII                        USD
POP-CARTS        POP                        USD


BARREL-CARTS        SamInc.               USD
BARREL-CARTS        BCI                   USD
BARREL-CARTS        RII                        USD
BARREL-CARTS        POP                  USD


I am firing a sql and getting back above data as List<ProductVO> like
List<ProductVO> completeProductList = db.getData();

ProductVO  is a bean defined as
public class ProductVO {
public String product;
public String type;
public String currency;
}
set(); methods
get(); methods

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my goal is to create a Map<String,List<ProductVO>> which contains data like this
Key                    value
IMAGE-CARTS     List<ProductVO>  -- the count of the list must be 4 (for each type and currency)
POP-CARTS       List<ProductVO>  -- the count of the list must be 4 (for each type and currency)
BARREL-CARTS    List<ProductVO>  -- the count of the list must be 4 (for each type and currency)


what i am doing is something like this

Map<String,List<ProductVO>> productMap = new HashMap<String,List<ProductVO>>();
List<ProductVO> tempList = new ArrayList<ProductVO>();

for (ProductVO productData: completeProductList){      //original list from query                  
                  String product = productData.getProduct();
                  tempList.add(productData);                  
                  productMap.put(product,tempList);  
            }
Now my productMap has 3 keys and each key has value as List<ProductVO> with count 12

Any idea how i can create a Map which contains  3 keys and each key has value as List<ProductVO> with count 4 ?
 
Thanks very much.
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Question by:royjayd
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2 Comments
 
LVL 27

Accepted Solution

by:
dpearson earned 500 total points
ID: 40401093
The problem you're having is that you're only creating 1 list.

You need to create 1 list for each key.

Something like this:

Map<String,List<ProductVO>> productMap = new HashMap<String,List<ProductVO>>();

for (ProductVO productData: completeProductList){      //original list from query                  
                  String product = productData.getProduct();
                  List<ProductVO> list = productMap.get(product) ;

                  // Create a list for this key if one does not already exist
                  if (list == null) {
                       list = new ArrayList<ProductVO>() ;
                       productMap.put(product,list);  
                  }

                  // By this point the list is always in the map so we can just add to it
                  list.add(productData);                  
            }

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0
 

Author Comment

by:royjayd
ID: 40401984
Thanks Doug. I appreciate your help.
Any help with my next question will be greatly appreciated.
http://www.experts-exchange.com/Programming/Languages/Java/Q_28543903.html
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