CODEWITHSUNDEEP
javaarraylist
Rakesh B
Rakesh B

Reputation: 47

How to access list of ArrayList elements

I have List of ArrayList Elements, see below.

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

it contains some array list elements.

eg.

x.get(0)->[1,2,3,4],
x.get(1)->([5,6,7,8],
x.get(2)->[9,10,11,12],
x.get(3)->[13,14,15,16]

i want to access element 3 from x.get(0) or element 7 from x.get(1) how to call that??

Upvotes: 2

Views: 13164

Answers (3)

Dave
Dave

Reputation: 69

//To directly access any list member using for loop instead of foreach loop

List<List<Integer>> list = new ArrayList<List<Integer>>();
for(int i=0;i<list.size();i++){
   for(int j=0;j<list.get(i).size();j++){
      do_something_on(list.get(i).get(j);
   }
}

Upvotes: 0

T.Gounelle
T.Gounelle

Reputation: 6033

Each element of your list is a list and has the same interface that provides List<T> methods, e.g.

  • T get(int index)
  • boolean isEmpty()
  • void add(T element)
  • etc.

You can access element from the inner list by index 

List<List<String>> x = new ArrayList<List<String>>();
// ... some data initialised
String element_0_3 = x.get(0).get(3);

Be aware that each List<String> element needs to have been created before accessing it. For instance, in order to add a new String at the [0,0] coordinates:

List<List<String>> x = new ArrayList<List<String>>();
List<String> x0 = new ArrayList<>();
x0.add("foo"); // add "foo" as the first string element
x.add(x0); // add x0 as the first List<String> element

You can also read values with an enhanced for loop, without using the indexes:

List<List<String>> x = new ArrayList<List<String>>();
//...
for (List<String> ls : x) { // iteration on the x list
   for (String s : ls) {    // iteration on each intern list
      System.out.println(s);
}

Upvotes: 2

Aninda Bhattacharyya
Aninda Bhattacharyya

Reputation: 1251

You can follow like...

List<List<String>> x = new ArrayList<List<String>>();
List<String> subX = x.get(7);
if(null != subX && subX.size() != 0) {
    String element = subX.get(0);
}

Upvotes: 0

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