在节点末尾添加新元素（Java）

Question

im having trouble adding elements to the end of my list. It keeps on adding to the beginning of the list. I've been at this for a while now, just stuck and lost.

public class RefUnsortedList<T> implements ListInterface<T> {

      protected int numElements;      // number of elements in this list
      protected LLNode<T> currentPos; // current position for iteration

      // set by find method
      protected boolean found;        // true if element found, else false
      protected LLNode<T> location;   // node containing element, if found
      protected LLNode<T> previous;   // node preceeding location

      protected LLNode<T> list;       // first node on the list

      public RefUnsortedList() {
        numElements = 0;
        list = null;
        currentPos = null;
      }

      public void add(T element) {
      // Adds element to this list.


        LLNode<T> newNode = new LLNode<T>(element);

        newNode.setLink(list);
        list = newNode;
        numElements++;

Here is my main class:

RefUnsortedList<Patient> patient1 = new RefUnsortedList<Patient>();
Patient entry;
entry = new Patient("Tam Ngo", "0848896");
patient1.add(entry);
entry = new Patient("Mike You", "0848896");
patient1.add(entry);

System.out.println(patient1.toString());

Answer 1

the add method in java has a second signature, which you can use: http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html#add(int , E)

You can specify where you want to add your next element

Answer 2

As is written, your list variable holds the first node on the list. Now, your add method includes the line:

list = newNode;

This line immediately sets the node you're adding to the beginning of the list!

A possible fix is to maintain two pointers: one to the beginning of the list (for searching through it) and one to the last element, let's say you call it last . In that case, to add a node you could do the following:

last.setLink(newNode);
last = newNode;

Here, we set a link from the current last node to the new node, and then make the new node the new last node.

Hope this helps!