Hi all I am facing a problem while using hibernate criteria query

My object structure as follows

StockBatch {
Long id;
String batchNumber;
Date batchdate;
Collection<Stock> stock;
Item item;
}

Stock {
Long id;
double quantity;
Unit atUnit;
String stockStatus;
}

Unit{

Long id,
String name,(e.g :Chenni)
String location
}

Item {

Long id,
String name, (e.g :N79 Mobile)
String code;
Double unitWeight
}

I tried to find quantity of N79 mobiles(item) in Chenni unit(atUnit). But i got the stock of N79 mobiles in Chenni,Kolkata,Mumbai units

I used Hibernate Criteria Query as below

public Collection<StockBatch> getStock(Item item,Unit atUnit)throws Exception{

Collection<StockBatch> stockBatckList = new ArrayList<StockBatch>();

Criteria criteria = getSession().createCriteria(StockBatch.class);

criteria.add(Expression.eq("item.id", item.getId())); // item id of N79

criteria.createCriteria("stock", "stockAlias");
criteria.add(Expression.eq("stockAlias.atUnit.id", unit.getId()); // unit id of Chenni

criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
stockBatckList = criteria.list();

return stockBatckList;
}


I was queried for quantity like below

Collection<StockBatch> stockBatchList = getStock(item,atUnit);

double StockQuantity =0.0;

for(StockBatch stockBatch : stockBatchList){

for(Stock stock : stockBatch.getStock()){

StockQuantity = StockQuantity+stock.getQuantity();
}
}

How it is possible to avoid the unwanted data ? is it possible by using any JOIN ?

Thanks in advance

What is the use of distinctRootEntity, is it solve this issue ?