Trying to understand more about the nodes and linkedlist in java

Question

I just began to learn LinkedLists and nodes and I don't understand something in this code :¸

public class ListeChainee<E> {

private Noeud debut=null;
private Noeud fin=null;
private int taille=0;

private class Noeud 
{
    private E contenu;
    private Noeud suivant;

    Noeud(E contenu, Noeud suivant)
    {
        this.contenu=contenu;
        this.suivant=suivant;
    }
}
public boolean add(E element)
{
    Noeud n= new Noeud(element,null);

    if(taille==0)
        debut= n;           
    else
        fin.suivant=n;      
    fin=n;
    taille++;
    return true;
}

And in my main class, i have this :

ListeChainee<Integer> liste= new ListeChainee<Integer>(); liste.add(2); liste.add(3);

I'm trying to understand why when I do "liste.add(3)", debut.suivant changes ? Thank you for your help

Answer 1

When you add 2, it is the first node in the list, thus debut point to it. but it has no successors, thus suivant is null.

When you add 3, 2 needs to point to 3, so 2's suivant link points to 3. it just so happens that since 2 is the first node, you see this change in debut.suivant, as debut and fin are the same node at this point.

Answer 2

debut.suivant changes when you execute "liste.add(3)" because debut and fin reference the same Noeud when the list contains a single Noeud, therefore inside the add method fin.suivant = n is the equivalent to debut.suivant = n when the second node is added.

Consider the following lines of code to understand why debut == fin for the first Noede of the list:

if(taille==0)
    debut= n;           
...  
fin=n;

Both debut and fin are assigned n, therefore when fin.suivant is changed in the second add, so is debut.suivant.