Printing a Heap of BinaryTrees...help!

Question

Ok, I have a tree full of BinaryTrees. I am 99% sure that my insert function works for inserting the BT's into the heap. I am getting a null pointer exception when I try to print the heap. Here is come of my code.
//Inserting the data into the heap.
for (int i = 0; i < letters.length; i++)
BinaryTree bt = new BinaryTree(letters);
bt.root.count = count[i];
heap.insert(bt);
//Printing the heap.
for (int i = 0; i < heap.array.length; i++)
System.out.println("[" + ((BinaryTree) heap.array[i]).root + "]: " + ((BinaryTree) heap.array[i]).root.count);
To explain some of this code.....
The input is a bunch of characters (ex. abbccccdddddd). It reads in a character and finds how every many of them there are (ex. a-1, b-2, c-4, d-6). Then, it will assign each character and its count to a root node in its own BinaryTree. Then the BinaryTrees are taken and stored in a Heap. I am getting a null pointer exception at the print statement. Any ideas?
-B

Answer 1

It is kinda late and Im tired and made some mistakes in the first line of my post. This is what it should be...
Ok, I have a HEAP full of BinaryTrees. I am 99% sure that my insert function works for inserting the BT's into the heap. I am getting a null pointer exception when I try to print the heap. Here is SOME of my code.