Thread: Binary Search Tree

Hello, I have to do Binary Search Tree. I found on internet a lot of versions, but i need it just simple. First time, I need help with method insert.
My code:

public class BinarySearchTree {
    private Node root;
    private Node parent;
    private Node node;
 
 
    public boolean isEmpty()
    {
        return root==null ;
    }
 
    public void insert(int number)
    {
          if(root==null)
           {
               Node newNode = new Node();
               newNode.setData(number);
               root=newNode;
           }  
    }
 
    public void remove(int)
    {
 
    }
 
    public boolean contains(int)
    {
        return;
    }
 
 
}

public class Node {
    private Node left;      //left children
    private Node right;     //right children
    private Node parent;
    private int data;
 
 
    public void setLeft(Node left)
    {
        this.left=left;
    }
    public Node getLeft()   
    {
        return left;
    }
 
    public void setRight(Node right)
    {
        this.right=right;
    }
 
    public Node getRight()
    {
        return right;
    }
 
    public void setParent(Node parent)
    {
        this.parent=parent;
    }
 
    public Node getParent()
    {
        return parent;
    }
 
    public void setData(int data)
    {
        this.data=data;
    }
 
    public int getData()
    {
        return data;
    }
}

Ohh yes. Thank you.
I wrote this code:

public boolean isEmpty()
    {
        return root==null ;
    }
 
   private Node insertData(Node node, int data)
{
    //insert code to check if node is null, if it is return a new node
    if (node==null)
    {
        return node;
    }
    //recursively go down the tree
    if ( node.getData() > data )
    {
         node.setRight(insertData( node.getRight(), data));//do insert on the right node
    }
    else
    {
         node.setLeft(insertData(node.getLeft(), data));//do insert on the left node
    }
    return node;
}
public void insert(int data)
{
   root =  insertData(root, data);
}

public class Main {
 
 
    public static void main(String[] args) {
        BinarySearchTree b1 = new BinarySearchTree();
 
        System.out.println(b1.isEmpty());
        b1.insert(10);
        b1.insert(5);
        b1.insert(3);
        b1.insert(12);
        b1.insert(14);
        System.out.println(b1.isEmpty());
 
    }
 
}

But it write:
true
true
Where is the problem?

In you're insert method you need to check for a null root node. Then, if it is null, create a new node.

no, like this:

public void insert(int data)
{
    if (root == null)
    {
          root = new Node(); // err, i'm not sure i know what you're node constructor looks like, but put it here
     }
     insertData(root, data);
}

I changed it:

public class BinarySearchTree {
    private Node root;
    private Node parent;
    private Node node;
 
 
    public boolean isEmpty()
    {
        return root==null ;
    }
 
   private Node insertData(Node node, int data)
{
    //insert code to check if node is null, if it is return a new node
    if (node==null)
    {
        return node = new Node();
    }
    //recursively go down the tree
    if ( node.getData() > data )
    {
         node.setRight(insertData(node.getRight(), data));//do insert on the right node
    }
    else
    {
         node.setLeft(insertData(node.getLeft(), data));//do insert on the left node
    }
    return node;
}
public void insert(int data)
{
    if (root==null)
    {
        root = new Node();
        insertData(root, data);
    }
    insertData(root, data);
}

Class Node:

public class Node {
    private Node left;      //left children
    private Node right;     //right children
    private Node parent;
    private int data;
 
 
    public void setLeft(Node left)
    {
        this.left=left;
    }
    public Node getLeft()
    {
        return left;
    }
 
    public void setRight(Node right)
    {
        this.right=right;
    }
 
    public Node getRight()
    {
        return right;
    }
 
    public void setParent(Node parent)
    {
        this.parent=parent;
    }
 
    public Node getParent()
    {
        return parent;
    }
 
    public void setData(int data)
    {
        this.data=data;
    }
 
    public int getData()
    {
        return data;
    }
}

But something is wrong. picture Ddebuger: Imageshack - debuga