How to put contents in hashmap with in hashmap

Question

I have contents in CSV file like this

User1,What is your favorite color?,color
User1,What is the name of your pet?,pet
User1,What is your mother's maiden name?,mother
User2,In what city were you born?,city
User2,What elementary school did you attend?,school
User2,What was your first best friend's name?,friend

I need to call OIM API which will take parameters like this

void setUserChallengeValues(java.lang.String userID,
                        boolean isUserLogin,
                        java.util.HashMap quesAnsMap)

where quesAnsMap parameter means HashMap of challenge question and answers

What is the efficient way of parsing the CSV file with hashmap of userid as key and question and answer as value?

My hashmap should be like User1 is key and value should have question as key and answer as value.

Any sample snippet to refer?

Thanks

score 2 · Accepted Answer · answered Apr 20 '16 at 10:52

Read the file line by line, spliting it by ',' using String.split()

HashMap<String, Map<String, String>> userAnswers = new HashMap<>();
BufferedReader reader = new BufferedReader(new FileReader("/PATH/TO/YOUR/FILE.cvs"));
String ln;
while((ln = reader.readLine()) != null)
{
    String [] split = ln.split(",");
    String user = split[0];
    Map<String, String> userMap = userAnswers.get(user);
    if(userMap == null)
    {
        userMap = new HashMap<String, String>();
        userAnswers.put(user, userMap);
    }

    userMap.put(split[1], split[2]);
}

reader.close();

Thanks this helped me to handle this properly. – user2961454 Apr 20 '16 at 20:00 — user2961454, Apr 20 '16 at 20:00

Vikrant Kashyap · Answer 2 · 2016-04-20T11:31:09.637

Here I am writing an method in which you can provide file (.csv) name as an parameter and get HashMap<String, String> as a Result

public Map<String, String> putYourCSVToHashMap(String prm_csvFile) {

BufferedReader br = null;    //bufferReader
String line = "";
HashMap<String,Map<String, String>> hMapData = new HashMap<>();
Map<String, String> userMap;  //refering to inner Hashmap.
String cvsSplitBy = ","; //parameter on which your csv lines is splitted as an Array.

try {   
   br = new BufferedReader(new FileReader(prm_csvFile)); // Read Your File and Stored into BufferedReader.

while ((line = br.readLine()) != null) { //read each Line of File till last.

    String[] csv_LineAsArray= line.split(cvsSplitBy); //each line will is splitted into an String Array.

    String username = csv_LineAsArray[0]; //pick username available at 0th Index.

    userMap= hMapData.get(username);

    if(userMap == null) //if perticular user doesnot have any record
      {
//Create a New Object for each new line where Question as a key Answer as a Value.
        userMap = new HashMap<String, String>(); 
        hMapData.put(user, userMap);
      }

    // put question as a key and Answer as a Value.    
     userMap.put(csv_LineAsArray[1], csv_LineAsArray[2]);
 }

    } catch (FileNotFoundException e) {
            e.printStackTrace();
    } catch (IOException e) {
            e.printStackTrace();
    } finally {
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return hMapData;   // return your csv file as a HashMap.
}

score 0 · Answer 3 · answered Apr 20 '16 at 11:50

I will tell you how I would do it, following the principle "Keep it as simple as possible".

I have read the other answers and I think using String.split is bad idea since you know exactly where to look for your values in each line of the CSV file. Much better approach would be to use substring.

So here is sort of complete solution.

We create the class Tuple to store Q/A tuple. ( I am no using map since its a overkill :) )

class Tuple {
public String question;
    public String answer;

    public Tuple(String question, String answer) {
        this.question = question;
        this.answer = answer;
    }
}

Its a simple class but it will save you lots of code later.

Now for the main class to do all the work.

class Questions { private final Map csvData;

    public Questions() {
        csvData = new HashMap<String, Tuple>();
    }

    public void setUserChallengeValues(String line) {
        String name = "";
        String question = "";
        String answer = "";

        name = line.substring(0, line.indexOf(","));
        line = line.substring(line.indexOf(",") + 1);
        question = line.substring(0, line.indexOf(","));
        line = line.substring(line.indexOf(",") + 1);
        answer = line;
        this.csvData.put(name, new Tuple(question, answer));
    }
}

There is your method, the logic is very simple (a lot simpler compared to split in my opinion). You just look for ","'s index. That way you can easily extract Name, Question and Answer from each line.

And finally the actual parsing becomes few lines of code.

  Questions questions = new Questions();

  //Feed the lines here one by one
  String line1 = "User1,What is your favorite color?,color";
  questions.setUserChallengeValues(line1);

Let me know if you need the whole code snippet.

Good luck :)

I can not pass new Tuple(question, answer) as third argument to Oracle API setUserChallengeValues as it expects the third parameter as HashMap only. how can I handle this leveraging your code? — user2961454, Apr 20 '16 at 15:09

How to put contents in hashmap with in hashmap

3 Answers3