CODEWITHSUNDEEP
javalistpointerslinked-listlistiterator
Palak Jain
Palak Jain

Reputation: 163

Change value of an element in a LinkedList in java

I defined a linked list of Candidate objects. I need to store the initial next element for every element (since I would be changing the order later, and require the initial order). 

public class Candidate {
    //data members
    private String prefrence;
    private Candidate next;
    public void setNext(Candidate c){ next=c; }
    //rest of the class body
}

In a separate class I need to create a list of candidates (candidateList) where I have to initialize it, 

while(input) {
    Candidate c = new Candidate(field[0], field[1], field[2], ...);
    candidateList.add(c);
}

Now, I need to store the next element of list in c.next. I also require to iterate over the entire list and change the preference of candidate in list. However, I don't know how to access the elements of the list.

Basically, I know the c++ equivalent where pointer to Candidate (ptr), ptr->datamember=abc; would do the job. But I am new to Java and can't get the hang of pointer mechanism here. I intend something like this:

ListIterator<Candidate> itr = candidateList.listIterator();
while(itr.hasNext()) {
    Candidate c = itr.next(); //I am supposing this creates a copy while i need a reference
    func(c.pref);
    c.pref = abc;
    c.next = def;
}

In short, I need to change the value of elements in a linked list and not change the element itself.

Upvotes: 1

Views: 3643

Answers (1)

Eran
Eran

Reputation: 393841

itr.next() of ListIterator of LinkedList doesn't create a copy. 

public E next() {
    checkForComodification();
    if (nextIndex == size)
    throw new NoSuchElementException();

    lastReturned = next;
    next = next.next;
    nextIndex++;
    return lastReturned.element;
}

It returns a reference to a Candidate object stored in the list. Therefore you can update the returned Candidate, which would update the Candidate object in the list.

Upvotes: 1

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