Question

I want to make just a simple function that sums all with same name.

I have mapped JDO like this:

costName    Cost     
food        10 
food        10
water       5
food        10

total of food 30
total of water 5

With this code I get total sum of all (this case 35)

int totalsum=0;
int sumCap=0;
for (JDO total : table) {

     totalsum += total.getCost() ;

}

How do I get the cost for only food or/and water?

Should be simple but I don’t get it.

Answer 1

Map<String, Integer> values = new HashMap<>();
for (JDO total : table){
   String name = total.getCostName();
   Integer val = values.get(name);
   if (val == null) val = 0;
   val += total.getCost();
   values.put(name, val);
}
int total = values.get("food");

The above calculates all totals in one pass and then allows you to retrieve any you desire. You could also look for a specific name in the loop and only add the values that match.