Storing strings in binary search tree
On the below code I get: ClassCastException : java.lang.String. I am trying to build a binary search tree from a text file one word at a time. when I call this method below the first time it works fine, but on the second call it gets the error at the second if statement:
http://rafb.net/paste/results/ieJkKd64.html
This is the code I use to call on the above function:
http://rafb.net/paste/results/j5MPDn59.html
Also, this interface is used by the insertBST function:
http://rafb.net/paste/results/0VQjVm42.html
[551 byte] By [
EzMea] at [2007-11-26 12:32:30]
Most people will not go to those unknown sites. Post a small working program that is an example of the problem here. Format your code between code tags, as explained in the Formatting tips link above the typing area.
> Most people will not go to those unknown sites. Post
> a small working program that is an example of the
> problem here.
>
> Format your code between code tags, as explained in
> the Formatting tips link above the typing area.
On the below code I get: ClassCastException : java.lang.String. I am trying to build a binary search tree from a text file one word at a time. when I call this method below the first time it works fine, but on the second call it gets the error at the second if statement:
public void insertBST(Object o) {
TreeNode p, q;
TreeNode r = new TreeNode(o);
if (root == null)
root = r;
else {
p = root;
q = root;
while (q != null) {
p = q;
System.out.println(r.getInfo());
if (((TreeComparable)(r.getInfo())).compareTo((TreeComparable)(p.getInfo())) < 0)
q = p.getLeft();
else
q = p.getRight();
}
if (((TreeComparable)(r.getInfo())).compareTo((TreeComparable)(p.getInfo())) < 0)
setLeftChild(p, r);
else
setRightChild(p, r);
}
}
This is the code I use to call on the above function:
public void readFromFile() {
//int i = 1;
while (fileScan.hasNext()) {
String buf = fileScan.next();
hash(buf);
if (table[tableIndex] == tableIndex) {
System.out.println("Same Omitted Word");
}
else{
obt.insertBST(buf);
System.out.println("Not an Omitted Word");
}
}
}
public int hash(String s) {
sum = 0;
for(int i = 0; i< s.length(); i++)
sum += (int)s.charAt(i);
tableIndex = sum%TABLESIZE;
return tableIndex;
}
-Also, this interface is used by the insertBST function:
public interface TreeComparable {
public int compareTo(Object o);
public void operate(Object o);
public void visit();
EzMea at 2007-7-7 15:45:32 >
A ClassCastException is thrown when you try and cast an object to a subclass of that is not an instance like shown in the example below:
Integer i = new Integer(5);
String s = (String)i;
String is not a subclass of Integer (ie: String does not extend the Integer class)
I assume getInfo returns a String, and then you are trying to cast that to a TreeComparable. Since String does not extend TreeComparable, it throws that exception.
Also, does your class implement TreeComparable? And why exactly do you have to cast it to a TreeComparable anyways? That really makes no sense
> A ClassCastException is thrown when you try and cast
> an object to a subclass of that is not an instance
> like shown in the example below:
>
> Integer i = new Integer(5);
> String s = (String)i;
>
> String is not a subclass of Integer (ie: String does
> not extend the Integer class)
>
> I assume getInfo returns a String, and then
> you are trying to cast that to a TreeComparable.
> Since String does not extend TreeComparable, it
> throws that exception.
>
> Also, does your class implement TreeComparable? And
> why exactly do you have to cast it to a
> TreeComparable anyways? That really makes no sense
It is true that getInfo returns a String. I have tried declaring the class where insertBST resides as:
public class ObjectBinaryTree implements TreeComparable{
but I got the above b]ObjectBinaryTree class from the profesor, so I'm not sure if changing it is the best way.
If I do the above changes I get :
ObjectBinaryTree is not abstract and does not override abstract method visit() in TreeComparable
if I make ObjectBinaryTree abstract other classes in the same project say ObjectBinaryTree can not be instantiated
EzMea at 2007-7-7 15:45:32 >
