[shadowdemon69]

Hello I get the following error when i try to run my program. I am new to java and pretty new to programming as well. So I don't understand these errors.
Edit: !!! I posted the wrong code I updated it with the code I am having problems with.

Exception in thread "main" java.lang.NullPointerException
	at BinarySearchTree.numGreaterThan(BSTEnhanced2.java:41)
	at BSTEnhanced.main(BSTEnhanced2.java:113)

class BinaryTreeNode {
	int element;
	BinaryTreeNode left;
	BinaryTreeNode right;
	int size;
	public BinaryTreeNode(int theElement) {
	element = theElement;
		left = null;
		right = null;
		size = 1;
	}
}

class BinarySearchTree {
	BinaryTreeNode root;

	public BinarySearchTree(){
	root = null;
	}

	public boolean search(int theElement) 
	{
	BinaryTreeNode x = root;
		while (x != null) {
		if (x.element == theElement) return true;
			if (x.element < theElement) x = x.right;
			else x = x.left;
	}
		return false;
	}

	public int numGreaterThan(int x){
		int counter = 0;
		BinaryTreeNode y = root;
		while(y != null) {
			if (y.element == x){
				counter = counter + y.right.size;
				
			}
			if (y.element > x){
				counter = counter + y.right.size;
				counter = counter++;
				y = y.left;
			}
			if (y.element < x){
				y = y.right;
			}
		}
		return counter;
		
	}
	public void insert(int theElement)
	{ 
		if (search(theElement)) return;

		if (root == null) {
		root = new BinaryTreeNode(theElement);
			return;
	}
	BinaryTreeNode x = root;
		boolean done = false;
		while (! done) {
			x.size = x.size + 1;
		if (x.element == theElement) return;
			if (x.element < theElement) {
		if (x.right == null) 
			{
			x.right = new BinaryTreeNode(theElement);
						done = true;
					}
		else 
					{ x = x.right; }
		}
		else {
				if (x.left == null) {
			x.left = new BinaryTreeNode(theElement);
					done = true;
		}
				else
					{ x = x.left;}
			}
	} 
	}

	public void printTree(){
	print(root);
	}

	public void print(BinaryTreeNode x) {
	if (x != null) {
		print(x.left);
			System.out.println(x.element + " : " + x.size);
			print(x.right);
		}
	}
}

class BSTEnhanced {
	public static void main(String [] args) {
	BinarySearchTree myTree = new BinarySearchTree();
		int e;

		for (int i = 0; i < 10; i++) {
		e = (int) (20 * Math.random());
			myTree.insert(e);
			System.out.println(e);
	}


		myTree.printTree();
		for (int i = 0; i < 10; i ++) {
			e = (int) (20 * Math.random());
			int result = myTree.numGreaterThan(e);
			System.out.println("Nodes Greater than " + e + " = " +result);
		}
		
		
	}
}

This post has been edited by shadowdemon69: 27 March 2009 - 08:51 PM

[Fuzzyness]

public int numGreaterThan(int x){
		int counter = 0;
		BinaryTreeNode y = root;
		while(y != null) {
			if (y.element <= x){
				y = y.right;
				}

Not positive, never used the BinaryTreeNode, but try making this to < from <=

if (y.element <= x){

[pbl]

Fuzzyness, on 27 Mar, 2009 - 07:47 PM, said:

public int numGreaterThan(int x){
		int counter = 0;
		BinaryTreeNode y = root;
		while(y != null) {
			if (y.element <= x){
				y = y.right;
				}

Not positive, never used the BinaryTreeNode, but try making this to < from <=

if (y.element <= x){

Good show Fuzzy