Deleting elements from a binary heap

Question

I have to create a binary heap class and perform various operations. Every operation works except deleteMin, which gives an "ArrayIndexOutOfBoundsException: -1" exception in every case I've tried. Supposedly it's coming from line 85, which I put a line comment next to in the code below.
     * Deletes the smallest element (the root) from the heap and returns that value.
     * The heap is then reordered so that it is still a valid heap.
     * @return the root of the heap, a T type value
    public T deleteMin(){
        if(size == 0)
            throw new MyException();
        T returnValue = arr[0];
        T item = arr[size-1];
        size--;
        int hole = 0;
        int newHole = newHole(hole, item);
        while(newHole < arr.length - 1){
            arr[hole] = arr[newHole];  // ERROR IS HERE?
            hole = newHole;
            newHole = newHole(hole, item);
        arr[hole] = item;
        return returnValue;
     * Gives the index of where the next hole in the heap will be.
     * @param hole the index of the current hole
     * @param item the last element in the heap
     * @return the index of the next hole to be checked
    private int newHole(int hole, T item){
        int newHole = -1;
        if(arr[2*hole + 1] != null || arr[2*hole + 2] != null){
            if(arr[2*hole + 2] == null){
                if((arr[2*hole + 1]).compareTo(item) < 0){
                    newHole = 2*hole + 1;
            else {
                int smallerItem;
                // may need >= param
                if((arr[2*hole + 1]).compareTo(arr[2*hole + 2]) > 0)
                    smallerItem = 2*hole + 2;
                else
                    smallerItem = 2*hole + 1;
                if((arr[smallerItem]).compareTo(item) < 0)
                    newHole = smallerItem;
        return newHole;
    }I know I set newHole = -1 in the private method, which may be the problem, but the pseudo code my teacher gave me says to do just that. She gave us the pseudo code using a heap of int, the code is designed for a generic, comparable class. The test class uses a heap<String>. I just can't see why the problem is arising. Can anyone see where I've gone wrong?
Edited by: sublimeph03nix on Apr 23, 2009 1:57 PM
Edited by: sublimeph03nix on Apr 23, 2009 2:03 PM

Answer 1

arr[hole] = arr[newHole]; // ERROR IS HERE?I'd say that I bet newHole == -1, so you're trying to access element -1 in the array, which of course is out of bounds.
You have heard about debuggers, haven't you?