Problems converting Integer object to type int

Question

Not sure what is going on here. Seems like an auto-boxing problem but I've been stuck on this for awhile and thought it might benefit me to stop stressing out and get some more experienced hands on this. The assignment is essentially implementing a BST and extending it to an implementation of an AVL and then running performance tests. To simplify things we can stick with using Integer as the generic.

The problem I am having is when comparing two Nodes. Autoboxing is not taking place and the intValue() method is not recognized.

public class BinaryNode<Integer> implements Comparable<Integer>
{
   Integer data;
   BinaryNode<Integer> leftChild;
   BinaryNode<Integer> rightChild;
   int height;

   BinaryNode(Integer data)
   {
      this(data, null, null);
   }

   BinaryNode(Integer data, BinaryNode<Integer> lt, BinaryNode<Integer> rt)
   {
      this.data = data;
      this.leftChild = lt;
      this.rightChild = rt;
   }

   public Integer getData()
   {
      return this.data;
   }

   public BinaryNode<Integer> getLeft()
   {
      return leftChild;
   }
   public void setLeft(BinaryNode newNode)
   {
      this.leftChild = newNode;
   }

   public BinaryNode<Integer> getRight()
   {
      return rightChild;
   }
   public void setRight(BinaryNode newNode)
   {
      this.rightChild = newNode;
   }

   @Override
   public int compareTo(BinaryNode<Integer> otherNode)
   {
      return this.getData() - otherNode.getData();
   }
}

Edit: Thanks for the quick feedback. It was just the sort of interaction I needed to look at this differently and understand the quirky behavior I was encountering. Unfortunately I am bound to make this BinaryNode a generic class but the trick was to swap out all of the with or as the book's conventions prefer to use .

The best solution was to change the BinaryNode<Integer> to BinaryNode<AnyType> and remove the compareTo from this class. Now that I am no longer overshadowing java.lang.Integer I can reliably use the Integer.compareTo method as I originally intended.

For the curious, here is the TreePrinter class that I have to interact with that uses the parameterized BinaryNode class. http://www.cs.sjsu.edu/~mak/CS146/assignments/3/TreePrinter.java

Don't use `a - b` to compare two integers. It looks smart, but it doesn't take integer overflow into account. Try comparing `Integer.MAX_VALUE` and `Integer.MIN_VALUE` this way, or just `-1` and `Integer.MAX_VALUE`. Instead, use `Integer.compare(int, int)`. It is implemented as `(x < y) ? -1 : ((x == y) ? 0 : 1)` — Erwin Bolwidt, Jun 29 '15 at 03:33
Thanks Sotirios Delimanolis, this does explain the behavior I'm running into. The assignment uses a print class that instantiates a BinaryNode object which is why I am using the generic type. Here is the the class I am to interact with, http://www.cs.sjsu.edu/~mak/CS146/assignments/3/TreePrinter.java. — Scot Matson, Jun 29 '15 at 03:40

score 1 · Accepted Answer · answered Jun 29 '15 at 03:29

1

In class BinaryNode<Integer>, Integer is a generic type parameter, not the Integer class.

change

public class BinaryNode<Integer> implements Comparable<Integer>

to

public class BinaryNode implements Comparable<Integer>

And change any appearance of BinaryNode<Integer> to BinaryNode.

If you wanted the BinaryNode class to takes a generic data type, you wouldn't write code specific to Integer data type (for example, return this.getData() - otherNode.getData() will never compile if getData() returns some generic type parameter T).

answered Jun 29 '15 at 03:29

Eran

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This is probably mostly right for what I am attempting to accomplish. While removing the type parameter did resolve the errors, I actually need to have the type parameter as part of my solution to the assignment. Can't say I agree with it but that is college for you. However this in combination with Soritos Delimanolis's link gave me enough understanding to put the pieces together. Much appreciated. – Scot Matson Jun 29 '15 at 03:56

Obicere · Answer 2 · 2015-06-29T03:31:51.783

1

public class BinaryNode<Integer> implements Comparable<Integer>

Says that you have a new generic type named Integer. This is not the java.lang.Integer. This is why you're having issues, because they are completely different.

As Soritos Delimanolis pointed out, it would be better to just drop the generic type altogether.

edited Jun 29 '15 at 03:31

answered Jun 29 '15 at 03:29

Obicere

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Problems converting Integer object to type int

2 Answers2