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>>();
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
newAL.clear() removes all elements from ArrayList.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
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.
arrayList.get(index).add(Integer);?