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It shows null pointer exception in Driver class, can anybody find me the error ??

public class Node {
	
	int iData;
	double dData;
	Node leftChild;
	Node rightChild;
	
	
	public void displayNode(){
		System.out.println(dData);
	}
	

	
}
public class Tree {
	private Node root; //the root of the tree
	
	
	public Node find(int key) // find node with given key
	{ // (assumes non-empty tree)
	Node current = root; // start at root
	while(current.iData != key) // while no match,
	{
	if(key < current.iData) // go left?
	current = current.leftChild;
	else
	current = current.rightChild; // or go right?
	if(current == null) // if no child,
	return null; // didn't find it
	}
	return current; // found it
	}
		
	
	
	public void insert(int id, double dd){
		Node newNode = new Node(); // make new node
		newNode.iData = id; // insert data
		newNode.dData = dd;
		if(root==null) // no node in root
		root = newNode;
		else // root occupied
		{
		Node current = root; // start at root
		Node parent;
		while(true) // (exits internally)
		{
		parent = current;
		if(id < current.iData) // go left?
		{
		current = current.leftChild;
		if(current == null) // if end of the line,
		{ // insert on left
		parent.leftChild = newNode;
		return;
		}
		} // end if go left
		else // or go right?
		{
		current = current.rightChild;
		if(current == null) // if end of the line
		{ // insert on right
		parent.rightChild = newNode;
		return;
		}
		} // end else go right
		} // end while
		} // end else not root
		} // end insert()
	
	public void delete(int id){}
	
	//various other methods
	
	public void inOrder(){ //utility function
		inOrderRead(root);
	}
	
	private void inOrderRead(Node localRoot){
		while(localRoot != null){
			inOrderRead(localRoot.leftChild);
			localRoot.displayNode();
			inOrderRead(localRoot.rightChild);
		}
	}
	
	
	
	
	
	
}

It shows here null pointer exception !

public class TreeApp {
	public static void main(String[]args){
		
		
		Tree theTree = new Tree();
		theTree.insert(50, 1.5);
		theTree.insert(41, 50.0);
		theTree.insert(11, 0.0);
		
		
		theTree.inOrder();
		
		
		
		
	}
}

i think something wrong with my functions,, please help its very urgent!!

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7 Years
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Last Post by JamesCherrill
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Please post the full NPE message with all the line numbers and the actual lines they refer to. Indenting the code properly will also help to identify problems.

This topic has been dead for over six months. Start a new discussion instead.
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