Non-static method help..

Question

Hello..
I am new to Java and trying to create a Binary Tree, however I have encountered an error "non-static methos cannot be referenced from static context?" and I am unsure how to correct it.. I have C++ background and am unfamiliar with this type of error?
My BTNode class:
public class BTNode
    private Object data;
    private BTNode left, right;
    public BTNode(Object initialData, BTNode initialLeft, BTNode initialRight)
            data = initialData;
            left = initialLeft;
            right = initialRight;
    public BTNode()
            { this(null, null, null); }
    public BTNode(Object newdata)
            { this(newdata, null, null); }
    //NODE methods
    public Object getData()                     //return and set data in node
            {return data;}
    public void setData(Object data)
            {this.data = data; }
    public BTNode getLeft()                 //return and set left child
            {return left; }
    public void setLeft(BTNode left)
            {this.left = left; }
    public BTNode getRight()                //return and set right child
            {return right; }
    public void setRight(BTNode right)
            {this.right = right; }
    public boolean isLeaf()                 //return true if this is leaf node
            {return (left == null)&&(right == null); }
// TREE Methods - for tree starting at this node
// get specific data from a tree
        public Object getLeftmostData()
        { if(left == null)
               return data;
          else
              return left.getLeftmostData(); }
        public Object getRightmostData()
              { if(right == null)
               return data;
          else
              return right.getRightmostData(); }
// print data in a tree
        public void inorderPrint()
                    if (left != null)
                        left.inorderPrint( );
                    System.out.println(data);
                    if (right != null)
                        right.inorderPrint( ); }
        public void preorderPrint()
                    System.out.println(data);
                    if (left != null)
                        left.preorderPrint( );
                    if (right != null)
                        right.preorderPrint( ); }
        public void postorderPrint()
                    if (left != null)
                        left.postorderPrint( );
                    if (right != null)
                        right.postorderPrint( );
                    System.out.println(data); }
// pretty print a tree
        //public void print(int depth);
//Interface for Nodes in Binary Tree (3)
//removing nodes from a tree
//returns reference to tree after removal of node
        public BTNode removeLeftmost()
                    if (left == null)                               // we are as deep as we can get
                        return right;                               // remove this node by returning right subt ree
                    else
                        {                                           // keep going down recursively
                            left = left.removeLeftmost( );
                                                                    // when done, return node that act ivated this
                                                                    // method as root of t ree
                            return this; }}
        public BTNode removeRightmost()
                    if (right == null)                               // we are as deep as we can get
                        return left;                               // remove this node by returning left subt ree
                    else
                        {                                           // keep going down recursively
                            right = right.removeRightmost( );
                                                                    // when done, return node that activated this
                                                                    // method as root of tree
                            return this; }}
//returns number of nodes in tree
        public static long treeHeight(BTNode root)
                    if (root == null)
                        return -1;
                    else
                        return 1 + Math.max(treeHeight(root.left),
                                treeHeight(root.right));
        public static long treeSize(BTNode root)
                if (root == null)
                    return 0;
                else
                    return 1 + treeSize(root.left) + treeSize(root.right);
//copying a tree: returns reference to root of copy
       // public BTNode treeCopy(BTNode root);
    public static BTNode insertNode(BTNode root, int key){
            if (root == null) // null tree, so create node at root
                return new BTNode(new Integer(key));
            Integer data_element = (Integer) root.data;
            if (key <= data_element.intValue())
                root.setLeft(insertNode(root.left, key));
            else root.setRight(insertNode(root.right, key));
                return root; }
    public static BTNode findNode(BTNode root,int key){
            if (root == null)
                return null; // null tree
            Integer data_element = (Integer) root.data;
            if (key == data_element.intValue())
                return root;
            else
            if (key <= data_element.intValue())
                return findNode(root.left, key);
            else return findNode(root.right, key); }
    public static BTNode removeNode(BTNode root, int key){
            if (root == null) return null;
                Integer data_element = (Integer) root.data;
            if (key < data_element.intValue())
                root.setLeft(removeNode(root.left, key));
            else if (key > data_element.intValue())
                root.setRight(removeNode(root.right,key));
            else { // found it
            if (root.right == null) root = root.left;
                else if (root.left == null) root = root.right;
                    else {                                         //two children
                            Integer temp = (Integer)
                            root.left.getRightmostData();
                            root.setData(temp);
                            root.setLeft(root.left.removeRightmost());
            return root; }
Main class:
import java.util.Random;
public class Lab21 {
    /** Creates a new instance of Lab21 */ 
     * @param args the command line arguments
    public static void main(String[] args) {
        int UpperLimit = 50000;
        int Num_Nodes = 500;
        Random generator = new Random();
        int TR_create = generator.nextInt(UpperLimit);
        Integer cast = new Integer(TR_create);                  // Needed to cast initial value to BTNode object
        BTNode Tree_Root = new BTNode(cast);                    // Creating root object
        BTNode result = new BTNode();                           // Creating new node object to use for tree
        result.insertNode(Tree_Root,TR_create);                 // Inserting first Node
        if (UpperLimit <=0)
                throw new IllegalArgumentException("UpperLimit must be positive: " + UpperLimit);
        if (Num_Nodes <=0)
                throw new IllegalArgumentException("Size of returned List must be greater than 0.");
        for( int x = 0; x < Num_Nodes; ++x)  
                int value = generator.nextInt(UpperLimit);
                result.insertNode(Tree_Root,value);
        //BTNode.inorderPrint();
        System.out.println("The height of this tree is " + BTNode.treeHeight(Tree_Root));
        System.out.println("The smallest number in the tree is " + BTNode.getLeftmostData());
}The error is occuring with the last line where I am trying to access getLeftmostData();
Any help would be apprecited with this..
Thankyou

Answer 1

User 557835:
You need to use the name of the instance rather than the name of the class. It should be something like this:System.out.println("The smallest number in the tree is " + result.getLeftmostData());User 135880