CODEWITHSUNDEEP
javaarraylist
manpreetSingh
manpreetSingh

Reputation: 724

How to add and retrieve the values in Arraylist of ArrayList

I know how to create an ArrayList of ArrayList, but how to add new ArrayList and add value to that particular ArrayList and how to retrieve the data from that list.

ArrayList<ArrayList<Integer>> arrayList = new ArrayList<ArrayList<Integer>>();

Upvotes: 2

Views: 25578

Answers (3)

Akash Thakare
Akash Thakare

Reputation: 22972

how to add new ArrayLists and ADD value to that particular ArrayList and how to RETRIEVE the data form that list.

    ArrayList<ArrayList<Integer>> arrayList=new ArrayList<ArrayList<Integer>>();
    ArrayList<Integer> newAL= new ArrayList<Integer>();
    arrayList.add(newAL);
    newAL.add(1);
    newAL.add(2);
    newAL.clear();      
    System.out.println(arrayList.get(0));
    //Changes persist in your arraylist

So after adding ArrayList you can manipulate newAL as ArrayList stores reference you don't need to fetch and set element from main arrayList.

To retrive data you can Iterate(Use ForEach Loop) over arrayList or you can do following

    Integer List0Item1=arrayList.get(0).get(1);//Get first element of list at 0
    arrayList.get(0).set(0, 10);//set 0th element of list at 0 as 10
    ArrayList<Integer> list10=arrayList.get(10);//get arraylist at position 10

Upvotes: 4

Eternal_Explorer
Eternal_Explorer

Reputation: 1145

It is a list of list where every object of the parent list is in turn a sublist.The code is something like below:

List<List<String>> mainList = new ArrayList<List<String>>();  

      List<String> sublist1 = new ArrayList<String>();  
      sublist1.add("State");
      sublist1.add("Country");
      sublist1.add("City");

      mainList .add(sublist1); 

      List<String> sublist2 = new ArrayList<String>();  
      sublist2.add("Sleep");
      sublist2.add("Suspend");
      sublist2.add("Wait");

      mainList .add(sublist2); 

      for(List<String> obj:mainList){ // iterate 
            for(String value:obj){

                System.out.println(value);
            }
        }

}
}
    Hope this will help to clear your doubt.

Upvotes: 2

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35557

You can try this

    ArrayList<ArrayList<Integer>> arrayList = new ArrayList<>();
    ArrayList<Integer> list1=new ArrayList<>();
    ArrayList<Integer> list2=new ArrayList<>();
    list1.add(1); // add to list
    list1.add(2);
    list2.add(3);
    list2.add(4);
    arrayList.add(list1); // add to list of list
    arrayList.add(list2);
    for(ArrayList<Integer> i:arrayList){ // iterate -list by list
        for(Integer integer:i){ //iterate element by element in a list

        }
    }

You can get element directly

  arrayList.get(0).get(0); // 0th list 0th value

adding value to 0th list

 arrayList.get(0).add(1);  // 1 will add to 0th index list-list1

Upvotes: 4

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