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Thread: copy() to copy the values of singly linked list1 to another linked list

  1. #1
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    Default copy() to copy the values of singly linked list1 to another linked list

    I have written copy() method to copy the data of one linked list to another. However, i am not able to get the output i really need help on this. i really need to know where the error is as the issue is its not displaying the output:

    public class Link
    {

    public int iData; // data item

    public Link next; // next link in list
    // -------------------------------------------------------------
    public Link(int id) // constructor
    {
    iData = id;

    }
    // -------------------------------------------------------------
    public void displayLink() // display ourself
    {
    System.out.print("{" + iData +"}");
    }

    } // end of class

    public class LinkList
    {

    private Link first; // reference to first link on list
    private Link last; // REFERENCE TO LAST LINK ON LIST
    // -------------------------------------------------------------
    public LinkList() // constructor
    {
    first = null; // no items on list yet
    }
    // -------------------------------------------------------------
    public boolean isEmpty() // true if list is empty
    {
    return (first==null);
    }
    // -------------------------------------------------------------
    // insert at start of list
    public void insertFirst(int id)
    {
    Link newLink = new Link(id);
    newLink.next = first; // newLink --> old first
    first = newLink; // first --> newLink
    }
    // -------------------------------------------------------------
    public LinkList copy()
    {
    LinkList L5 =new LinkList();
    Link current= first;

    int x;

    while(current!=null) // i think something is wrong here
    {
    x=current.iData;

    L5.insertFirst(x);
    current=current.next;
    }
    return L5;
    }

    public static void main(String[] args)
    {
    LinkList L1 = new LinkList(); // make new list
    L1.insertFirst(22); // insert four items
    L1.insertFirst(44);
    L1.insertFirst(66);
    L1.insertFirst(88);
    L1.insertFirst(99);
    L1.displayList(); // display list

    LinkList Lcopy=new LinkList();
    System.out.println("-----------------Copied data in new list is:------------");
    Lcopy.copy();
    Lcopy.displayList();
    }
    }



    the output is :

    List (first-->last): {99}{88}{66}{44}{22}
    -----------------Copied data in new list------------
    List (first-->last):

    the values are not getting copied to another linked list.

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: copy() to copy the values of singly linked list1 to another linked list

    How are you trying to debug the code? Add some print statements in the copy method that print out the contents of variables as the method is executed.

    Please edit your post and wrap your code with code tags:

    [code]
    **YOUR CODE GOES HERE**
    [/code]

    to get highlighting and preserve formatting.

    the values are not getting copied to another linked list.
    How does the copy method know what to copy?
    If you don't understand my answer, don't ignore it, ask a question.

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