Nested Array list in Java

Question

I am asking user candidate info then i am calling 'addcandidate' method and i am trying to hold candidate info in array list.By the way if user want to add new candidate i am getting again their info and want to add my arraylist.But its holding only last candidate info

my addcandidate method code like this

static  void addcandidate(String name,String surname,String adress,String talent){
    List<List<Object>>listoflist=new ArrayList<>();
    List<Object>candidatelist=new ArrayList<Object>();
    candidatelist.add(name);
    candidatelist.add(surname);
    candidatelist.add(adress);
    candidatelist.add(talent);
    listoflist.add(candidatelist);
    

    System.out.println(listoflist);

}

and also mycode that to ask candidate info like that

  while (true){
        Scanner oku=new Scanner(System.in);
        System.out.println("what kind of process do you want ? 1-Add Candidate 2-Add Employee " +
                "3- add employee from candidate 4-search candidate for talent 5-print wiew");
        int processtype=oku.nextInt();

        if (processtype==1){
            System.out.println("please enter candidate name");
            String cname=oku.next();
            System.out.println("please enter candidate sname");
            String csname=oku.next();
            System.out.println("please enter candidate adress");
            String cadress=oku.next();
            System.out.println("please enter candidate talent");
            String ctalent=oku.next();
            Candidate.addcandidate(cname,csname,cadress,ctalent);
            System.out.println("do you want to continue");
            String answer=oku.next();
            if (answer=="n"){
                break;
            }


        }
    }

my output expectation is like this [[tom,jhn,usa,it],[peter,parker,england,language]]

listOflist is only stored in a local variable in addcandidate, and you create a new list each time you call addcandidate. — tgdavies
– tgdavies, Commented Aug 6, 2020 at 4:44
thank you for your answer but how can i create new list each time call addcandidate can you give example please — Basit Anlat
– Basit Anlat, Commented Aug 6, 2020 at 4:51
I mean that's what you are doing at the moment. You need to add the candidates to a list whose lifetime is the same as your entire program. — tgdavies
– tgdavies, Commented Aug 6, 2020 at 4:54

Lokoba · Accepted Answer · 2020-08-06 04:53:09Z

2

You need declare listoflist out of method addcandidate. For example like this.

import java.util.ArrayList;
import java.util.List;

public class Main {

    public static List<List<Object>> listoflist = new ArrayList<>();

    public static void main(String[] args) {
        addcandidate("Name 1", "Surname 1", "Street 1", "Music");
        addcandidate("Name 2", "Surname 2", "Street 2", "Singing");
        addcandidate("Name 3", "Surname 3", "Street 3", "Sport");
    }

    public static void addcandidate(String name, String surname, String adress, String talent){
        List<Object> candidatelist = new ArrayList<Object>();
        candidatelist.add(name);
        candidatelist.add(surname);
        candidatelist.add(adress);
        candidatelist.add(talent);
        listoflist.add(candidatelist);


        System.out.println(listoflist);

    }
}

The result of executing this code.

[[Name 1, Surname 1, Street 1, Music]]
[[Name 1, Surname 1, Street 1, Music], [Name 2, Surname 2, Street 2, Singing]]
[[Name 1, Surname 1, Street 1, Music], [Name 2, Surname 2, Street 2, Singing], [Name 3, Surname 3, Street 3, Sport]]

answered Aug 6, 2020 at 4:53

Lokoba

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2 Comments

Basit Anlat Over a year ago

Thank you so much very good it's working I appreciate

Lokoba Over a year ago

@BasitAnlat Welcome, I'm glad to hear that my answer was useful.

Dexter · Accepted Answer · 2020-08-06 05:11:25Z

1

Your listoflist declaration is inside addCandiadte method so each time the array list is being created and finally you are having the list that was created last. Do something like below:

// outside addCandiadte method
 List<List<Object>>listoflist=new ArrayList<>();

static  void addcandidate(String name,String surname,String adress,String talent){
   
    List<Object>candidatelist = new ArrayList<Object>();    
    
    candidatelist.add(name);
    candidatelist.add(surname);
    candidatelist.add(adress);
    candidatelist.add(talent);
    
    listoflist.add(candidatelist);
    

    System.out.println(listoflist);

}

Hope you got the point. Additionally use List<String>candidatelist instead of List<Object>candidatelist for better readability and type checking.

edited Aug 6, 2020 at 5:11

answered Aug 6, 2020 at 4:58

Dexter

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2 Comments

Basit Anlat Over a year ago

Thank you so much I appreciate all of you

Dexter Over a year ago

Hi @Basit Anlat, glad to help you. Please "Accept" one answer so that it will help other readers on SO. You can also vote multiple answers. stackoverflow.com/help/someone-answers

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