Vector of linked list

Question

How to create vector of linked list in Java using Collections? So far I have written the following code:

Vector <LinkedList <Integer> > adj = new Vector<>();

However I am unable to figure out how to initialize the vector with head nodes of the linked list.

What I want is given an integer N, I wish to initialize the vector with the values 0 to N-1 as the head nodes:

e.g given N = 4

vector ---> 0
            1
            2
            3 

So that later I can add members to the list when needed like :

vector ---> 0->2->3
            1->3
            2->0->1
            3->1 

Answer 1

With the code you have written, you have created an empty vector - you have to fill it with desired number of LinkedList instances (I am guessing you are a C++ programmer, where the vector would initialize "automatically"?). E.g. initialize your vector like this:

int N = 4;
Vector<LinkedList<Integer>> adj = new Vector<>(N); // N here isn't really needed, but it sets the initial capacity of the vector
for (int i = 0; i < 4; i++) {
    ajd.add(new LinkedList<>());
}

Also, as Turing85 pointed out, you should use ArrayList if you don't need the synchronization.