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Thread: Unchecked conversion error

  1. #1
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    Default Unchecked conversion error

    warning: [unchecked] unchecked conversion

    found: java.util.LinkedList
    requried: java.util.LinkedList<ListNode>

    LinkedList<ListNode> list = new LinkedList<>;

    and it has the ^ sign under the word "new"

    The above is the warning message i get when i use the command javac.exe -Xlint:unchecked *.java

    ListNode = a separate class i wrote in order to create ListNode objects. Basically i am inserting a ListNode object into each index of the LinkedList. However im getting many problems when attempting to run my program and i think it may have something to do with the ListNode class that i wrote.


    class ListNode
    {
    	private int coefficient;
     
    	private int power;
     
     
     
    //Constructor
     
    	public ListNode(int coefficient, int power)
    	{
     
    		this.coefficient = coefficient;
     
    		this.power = power;
     
    	}
     
    	public ListNode(int degree)
    	{
    		power = degree;
    	}
     
            public void changePower(int power)
    	{
    		this.power = power;
    	}
     
    	public void changeCoefficient(int coefficient)
    	{
    		this.coefficient = coefficient;
    	}
     
     
    //Accessor methods
     
    	public int getPower()
    	{
    		return power;
    	}
     
    	public int getCoefficient()
    	{
    		return coefficient;
    	}
    }

    Im not sure if i've provided enough info on the problem. If you want to see the other class where i actually use the ListNode class then you can ask and ill post it up (its quite long however, 250 lines).


  2. #2
    Super Moderator Sean4u's Avatar
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    Default Re: Unchecked conversion error

    It doesn't have anything to do with your ListNode class. You should copy and paste your error messages, I'd say you've mistyped the one in your original post. What you probably have in your source, if you've only got a warning, is:
    LinkedList<ListNode> list = new LinkedList(); // not <>
    The 'unchecked conversion' here is because you've used Generics 'LinkedList<ListNode>' to declare the list reference, and a plain old non-Generics instantiation of a LinkedList. Javac is warning you that your newly-created LinkedList may not contain objects of class ListNode, because you haven't explicitly said it does.

  3. #3
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    Default Re: Unchecked conversion error

    Polynomial.java:12: warning: [unchecked] unchecked conversion
    found : java.util.LinkedList
    required: java.util.LinkedList<ListNode>
    LinkedList<ListNode> list = new LinkedList();
    ^
    1 warning

    Polynomial = the class that i am attempting to use LinkedList and ListNode together in

    I have little experience with LinkedLists, but i think they are similar to ArrayLists. I thought that by typing LinkedList<ListNode> i would explicitly say that the linked list would only contain objects of the type ListNode

  4. #4
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    Default Re: Unchecked conversion error

    If you want to store Polynomial objects in your list then the code would be
    LinkedList<Polynomial> list = new LinkedList<Polynomial>();
    Improving the world one idiot at a time!

  5. #5
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    Default Re: Unchecked conversion error

    Oh nono thats not what im trying to do.

    polynomial_task.jpg

    So basically I create a polynomial object. Inside each polynomial object is just 1 Linked List. Placed on each index of the linked list is an object ListNode (which i had to write a class for). And its the ListNode that stores the data.

  6. #6
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    Default Re: Unchecked conversion error

    LinkedList<Polynomial> list = new LinkedList<Polynomial>();

    I didnt have the underlined part, and thats stopped the warning from appearing whenever i compile. Thnx guys for the help.

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