How to map two csv column with respect to their values in Java?

Question

I am a new bee in Java and want to map CSV columns according to their values. My orignal csv data is like:

 name,salary,address
 AAA,1000,kkk
 BBB,880,lll
 AAA,90,kkk
 CCC,700,mmm
 BBB,700,lll

Expected output should be in Hashmap Key Value pair of two columns name and salary like:

Key: AAA Value 1090
Key: BBB Value 1580
Key: CCC Value 700

This is my code:

        String line = "";
 InputStreamReader inStream = new 
       InputStreamReader(uc.getInputStream());
        buff = new BufferedReader(inStream);  
         try {
            while ((line = b.readLine()) != null) {
                String[] fields = parseCsvLine(line);

                // I dont know what to do here



            }


            b.close();
            Log.d("Get data from API", "Processing Stop");
        } catch (IOException e) {
            e.printStackTrace();
        }

 public  String[] parseCsvLine(String line) {
    // Create a pattern to match breaks
    Pattern p =
            Pattern.compile(",(?=([^\"]*\"[^\"]*\")*(?![^\"]*\"))");
    // Split input with the pattern
    String[] fields = p.split(line);
    for (int i = 0; i < fields.length; i++) {
        // Get rid of residual double quotes
        fields[i] = fields[i].replace("\"", "");
    }
    return fields;
}

Answer 1

What you want is to split your line data into part. Then accumulate it to a Map

Map<String, Integer> result = new HashMap<>();

while ((line = b.readLine()) != null) {
   String[] parts = line.split(","); // Split your line, take `,` as delimeter
   String key = parts[0]; // This is your 'AAA'
   Integer value = Integer.parseInt(parts[1]); // This is your 1000
   if (result.get(key) == null) {
       result.put(key, value); 
   } else {
       result.put(key, result.get(key) + value); // There's already a value here, add it with new value
   }


}

The ugly part:

   if (result.get(key) == null) {
       result.put(key, value); 
   } else {
       result.put(key, result.get(key) + value); // There's already a value here, add it with new value
   }

Can replaced with new Java 8 Map utility:

 result.putIfAbsent(key, value); // Put (key, value) if key is absent from the map
 result.compute(key, value, (k, v) -> v + value);