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Thread: Writing clone() method for LinkedList

  1. #1
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    Default Writing clone() method for LinkedList

    Hello, JPF. I am trying to implement my own LinkedList and the clone method I have written doesn't seem to work. Can anyone tell me what I did wrong? Thanks!

    Okay, this is what I have in my tester:
    import java.util.*;
    public class OurLinkedListTest
    {  public static void main (String [] args)
       {  try
         {
          OurLinkedList <String> myList = new OurLinkedList<String>();
          myList.add("A");
          myList.add("B");
          myList.add("C");
          myList.add("B");
          myList.add(2, "X");
          myList.addFirst("Y");
          myList.addLast("Z");
          OurLinkedList <String>cloned = (OurLinkedList<String>)myList.clone();
       }
       catch(IllegalStateException e)
       {  System.out.println("Rule #2 is violated.");
       } 
    }
    }

    public Object clone()
      {
         LinkedList<String> clone = new LinkedList<String>();
         for (int i=0; i<size; i++)
         {
            clone.add(get(i));
         }
         return clone;
      }
    Last edited by vluong; October 26th, 2009 at 07:05 PM.


  2. #2
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    Default Re: Writing clone() method for LinkedList

    Why does your clone method repeatedly (assuming size is greater than 1) add "A" into the cloned list and not the values of the list it is cloning?

  3. #3
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    Default Re: Writing clone() method for LinkedList

    literallyjer, the "A" are just used for testing and I forgot to change it before posting (it's been changed). I get this error:

    Exception in thread "main" java.lang.ClassCastException: java.util.LinkedList
    at OurLinkedListTest.main(OurLinkedListTest.java:14)

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    Default Re: Writing clone() method for LinkedList

    I am assuming that line 14 is this:

    OurLinkedList <String>cloned = (OurLinkedList<String>)myList.clone();

    If that's the case, then you are trying to cast a LinkedList into your OurLinkedList. Look closer at your clone method. You are cloning an OurLinkedList into a LinkedList and then trying to cast the LinkedList into an OurLinkedList.

  5. The Following User Says Thank You to literallyjer For This Useful Post:

    vluong (October 26th, 2009)

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    Default Re: Writing clone() method for LinkedList

    Thanks a bunch, literallyjer! It works now!

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    Default Re: Writing clone() method for LinkedList

    You are very welcome :-)

  8. #7
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    Default Re: Writing clone() method for LinkedList

    You should also implement Cloneable.

    // Json

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