Question

I am to java and I am trying to implement a remove from double linked list method but I am struggling and not sure how to advance. The method removes data stored at the given node in the list. I have read that I need to account for cases where the the element being removed is the start or end but I am not sure how to go about. In general I am not sure if this is the right way to do it. My code/progress is posted below. If any could help, it would be appreciated. Thanks

P.S. I have a start and an end reference within the class and a size reference

 public type removeAtTheIndex(int index) 
  {
     type theData = null;
    Node <type> current= start;
    Node temp= new Node();
    if (index >= 0 && index < size && start !=null)
    {

        for (int i=0; i < index && current.getNext()!= null; i++)
        {
            current=current.getNext();
        }
        if (current != null)
        {
        if (current == start)
        {

        }

        else if (current == end)
        {

         }

        else
        {
            theData= current.getData();
            temp= current.getPrev();
            temp.setNext(current.getNext());
            current.getNext().setPrev(temp);
            current.setData(null);
            size--;

        }

    }

    return theData;
}

Answer 1

I have changed the type to Type. Using lowercase for class names is not recommended in Java. I have added loads of comments in the hope that you will understand what is going on.

Note that this is not tested code. You may find bugs in it but I am confident that the essence of process is there.

public Type removeAtTheIndex(int index) {
  // I want to return the data that was removed.
  Type theData = null;
  // Sanity checks.
  if (index >= 0 && index < size && start != null) {
    // Find the entry with the specified index.
    Node<Type> current = start;
    for (int i = 0; i < index && (current = current.getNext()) != null; i++) {
    }
    // Did we find it?
    if (current != null) {
      // Yes! Gather the contents.
      theData = current.getData();
      // Clear it.
      current.setData(null);
      // Special?
      if (current == start) {
        // Its the start one.
        start = start.getNext();
        // Detach it.
        start.setPrev(null);
      } else if (current == end) {
        // Step end back one.
        end = end.getPrev();
        // Detach it.
        end.setNext(null);
      } else {
        // Remove from within list.
        Node prev = current.getPrev();
        // Point it at my next.
        prev.setNext(current.getNext());
        // Point my next to new prev.
        current.getNext().setPrev(prev);
      }
      // One less now.
      size--;
    }
  }
  return theData;
}