HashMap和ArrayList值的总和（来自CSV）

Question

I'm trying to make a java program where I first read the lines from csv file then add the second column to hashmap and the third column is the value.

There are duplicate product_id's (second column) in the file which have different values so I have added the values to array list. Now i have to figure out how to actually sum these values from arraylist and then write the output to csv file (new).

Input CSV (just the beginning of file):

466152;Product_69105;1
466152;Product_69133;6
466152;Product_69214;2
466152;Product_69216;2
466154;Product_01007;1
466154;Product_01083;1
466154;Product_01136;1
466154;Product_01155;1
466154;Product_01488;1
466154;Product_01491;1
466154;Product_01499;2
466154;Product_01513;1
466154;Product_01593;1
466154;Product_01646;1
466154;Product_01656;1
466154;Product_01688;1
466154;Product_01703;1
466154;Product_01770;1
466154;Product_01804;1
466154;Product_01909;1

.....

My output now:

Product_03067 [2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 2]
Product_82332 [1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 3, 2, 1, 2, 1, 1, 2, 1, 1]
Product_69594 [1, 1, 1, 1, 1, 1, 2, 2, 1, 1]
Product_82330 [1, 1, 1, 1, 3]
Product_03618 [1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 2, 2, 3, 1, 1, 1, 1, 
2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2]

....

Wanted output:

Product_03067, 20
Product_82332, 29
Product_69594, 12
Product_82330, 7

.....

Public class Tilausmäärä {

Map<String, List<Integer>> tuotteet;
String Tilausrivit = "tilausrivit.csv";
String Tilausrivit_2 = "abc.csv";

public Tilausmäärä() throws FileNotFoundException, IOException {
    tuotteet = new HashMap<>();
    readTilausrivitFile();
}

  public void readTilausrivitFile() throws FileNotFoundException, IOException {

    BufferedReader in = new BufferedReader(new FileReader(Tilausrivit));
    String line;

    while ((line = in.readLine()) != null) {
        String columns[] = line.split(";");
        String key = columns[1];
        int valueInt;
        List<Integer> valueList = null;

        try {
            valueInt = Integer.parseInt(columns[2]);
        } catch (NumberFormatException e) {
            System.out.println(e);
            continue;
        }

        if (tuotteet.containsKey(key)) {
            valueList = tuotteet.get(key);
        } else {
            valueList = new ArrayList<>();
            tuotteet.put(key, valueList );    
        }
        valueList.add(valueInt);

    } 

    in.close();
}

public static void main(String[] args) {
    try {
        Tilausmäärä tm = new Tilausmäärä();
        for (String k : tm.tuotteet.keySet()) {
            System.out.println(k + " " + tm.tuotteet.get(k));
        }


    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

Could use some help so any good ideas appreciated.

Thanks!

Answer 1

There are duplicate product_id's (second column) in the file which have different values so I have added the values to array list.

You could direct sum the values with the same product id.
The lists you are using don't seem required.

Your tuotteet map that is probably declared as Map<String, List<Integer>> could be Map<String, Integer> where the Integer value would be the sum.

The actual code where you populate the ArrayList :

 if (tuotteet.containsKey(key)) {
     valueList = tuotteet.get(key);
 } else {
     valueList = new ArrayList<>();
     tuotteet.put(key, valueList );    
 }
 valueList.add(valueInt);

could be :

  Integer actualValue = tuotteet.get(key);
  if (actualValue == null){
      tuotteet.put(key, valueInt);    
  }    
  else {
      tuotteet.put(key, actualValue + valueInt);    
  }

Answer 2

From what I understand from your code (a part of it is missing), you should have the total number as a value in the tuotteet map (whose definition is missing from the code you posted) and not the list. If the element is already in the map, you should increment its value, otherwise you should set its value to the current value.

Something like this:

Map<String, Integer> tuotteet;
...
    try {
        valueInt = Integer.parseInt(columns[2]);
    } catch (NumberFormatException e) {
        System.out.println(e);
        continue;
    }

    Integer val = null;
    if (tuotteet.containsKey(key)) {
        val = tuotteet.get(key) + valueInt;
    } else {
        val = valueInt;
    }
    tuotteet.put(key, val );