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Thread: T and <T>

  1. #1
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    Default T and <T>

    I am learning generics in my Data Structures class and during the reading I fully understand it but when it comes for me to write my own code and imlement it via a project or assignment, it takes me forever because I have to go back through the book and find spots where it applies to what I'm doing.

    Anyways, I have a code piece:

    public class TelephoneBinaryTree<T extends Integer> implements BinaryTreeADT<T> 
    {
    	TelephoneTreeNode<T> root;
     
    	int size;
     
    	public TelephoneBinaryTree()
    	{
    		size = 0;
    	}
     
     
    	public TelephoneBinaryTree(int a, int b, int c)
    	{
    		root = new TelephoneTreeNode<>(a, b, c);
    		size = 1;
    	}
     
    	public  T getRoot() 
    	{
    		return root; //Type mismatch: cannot convert from TelephoneTreeNode<T> to T
    	}

    Why does it give me a mismatch? I cannot find anywhere that explains this.

  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: T and <T>

    TelephoneTreeNode<T> isn't a T. You have 2 choices: change the return result to be a TelephoneTreeNode<T>.

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    Default Re: T and <T>

    I don't get it, why isn't it a T?

  4. #4
    Super Moderator curmudgeon's Avatar
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    Default Re: T and <T>

    Quote Originally Posted by that_guy View Post
    I don't get it, why isn't it a T?
    Because it's not, pure and simple. When you create an ArrayList<String>, the object created isn't a String, is it? You seem to be implying that it should be.