Java LinkedList删除最后一个节点

Question

I have a Java class which consists of a node list, WordNode , which has the attributes of the class Word and a WordNode object called next used as reference to the next node, as follows:

class WordNode
{
    Word word;
    WordNode next;

    WordNode(Word w)
    {
        word = w;
        next = null;
    }

    Word getWord()
    {
        return word;
    }
}

And the class Word has a String called name :

class Word 
{
    String name;

    Word(String n)
    {
            this.name = n;
    }

    public String getName()
    {
            return name;    
    }

    public void setName(String n)
    {
        name = n;
    }
}

I have a class which is a custom LinkedList to which I must add and remove words by specifying the word name. I am able to add without problems, but when I want to delete I have some issues. Below is the method to delete:

boolean remove(Word w)
{
    WordNode wm = new WordNode(w);

    if (list == null) return false; //can't delete on an empty list
    else
    {
        WordNode aux = list;

        while(aux != null)
        {
            if (wm.word.getName().compareTo(aux.word.getName()) == 0 ) //if the word to delete is found
            { 
                if (aux.next == null) //to erase the last element
                {
                    aux = null;       
                }
                else
                {
                    aux.word.setName(aux.next.word.getName()); //set current node's name to equal next node's

                    WordNode temp = aux.next.next;
                    aux.next = null; //to erase current node
                    aux.next = temp; //re-refer
                }                        
                return true;
            }
            else aux = aux.next;
        }

        return false; //reachable if word is not found
    }
}

Where list is supposed to be the LinkedList that holds all the nodes. aux is an auxiliary list that will cycle through the list to avoid un-linking. So, if I choose to remove a WordNode I compare names. It is actually removing well when the node is at any place, except the last node:

if (aux.next == null) //to erase the last element
{
    aux = null;       
}

I'm hoping to make that node null to mark a new end to the list, but it doesn't get erased. What could I change to erase the last element? Thank you for any help/suggestions in advance

Answer 1

You have to clear the WordNode's "next" pointer. As you don't have a "previous" pointer, you have to keep track of the previous WordNode manually.

boolean remove(Word w)
{
    WordNode wm = new WordNode(w);

    if (list == null) return false; //can't delete on an empty list
    else
    {
        WordNode aux = list;
        WordNode prev = aux;

        while(aux != null)
        {
            if (wm.word.getName().compareTo(aux.word.getName()) == 0 ) //if the word to delete is found
            { 
                if (aux.next == null) //to erase the last element
                {
                    prev.next = null;
                    // Takes care of the case of a one-item list
                    aux = null;
                }
                else
                {
                    aux.word.setName(aux.next.word.getName()); //set current node's name to equal next node's

                    WordNode temp = aux.next.next;
                    aux.next = null; //to erase current node
                    aux.next = temp; //re-refer
                }                        
                return true;
            }
            else {
                prev = aux;
                aux = aux.next;
        }

        return false; //reachable if word is not found
    }
}

Answer 2

Add a head node. Then in your check for last node you will have:

if (aux.next == null) //to erase the last element
{
   aux.head.next = null;
}