Binary tree problems.

hi everyone.
I have an assignment to use a binary search tree whose nodes hold a reference to a string, and also to an int which is the count of how many times that word occurs in an input file, then it traverses the tree and prints out the result to an output file.
But when I compile, I get this one error, which I'm not sure how to fix.
the error says:
WordCount2.java:142: displayNode(java.lang.String,int) in Node cannot be applied to () localRoot.displayNode();
and here's he code:
import java.io.*;
import java.util.*;
import java.util.StringTokenizer;
import java.lang.String.*;
class WordCount2
public static void main (String [] args) throws IOException
StringTokenizer tokenizer;
String inputpath, outputpath;
String line = "";
String str = "";
Tree tree = new Tree();
int i = 0;
int count = 0;
Node now = new Node();
BufferedReader stdin= new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the pathname of the input file: ");
inputpath = stdin.readLine();
System.out.println("Enter the pathname of the output file: ");
outputpath = stdin.readLine();
FileReader textFile1 = new FileReader(inputpath);
BufferedReader inputFile = new BufferedReader (textFile1);
FileWriter textFile2 = new FileWriter(outputpath);
PrintWriter outputFile = new PrintWriter(textFile2);
while ((line = inputFile.readLine()) != null)
tokenizer = new StringTokenizer(line, " ");
while (tokenizer.hasMoreTokens())
String s = tokenizer.nextToken().toLowerCase();
tree.insert(s, i);
tree.inOrderTraverse(now);
class Node
public String sData;
public int iData;
public Node leftChild;
public Node rightChild;
public Node()
sData = "";
iData = 0;
public void displayNode(String s, int i) throws IOException
String file = "test1.txt";
FileReader fr = new FileReader (file);
BufferedReader inFile = new BufferedReader(fr);
String line = inFile.readLine();
String file2 = "outfile.txt";
FileWriter fw = new FileWriter (file2);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter outFile = new PrintWriter(bw);
outFile.print (s);
outFile.print (" - ");
outFile.print (i);
outFile.flush();
class Tree
private Node root;
public Tree()
root = null;
public void insert(String sd, int id)
Node newNode = new Node();
newNode.sData = sd;
newNode.iData = id;
if (root == null)
root = newNode;
else
Node current = root;
Node parent;
while (true)
parent = current;
if ((newNode.sData).compareTo(current.sData) < 0)
current = current.leftChild;
if (current == null)
parent.leftChild = newNode;
return;
else if((newNode.sData).compareTo(current.sData) == 0)
increment(newNode.iData);
else
current = current.rightChild;
if(current == null)
parent.rightChild = newNode;
return;
public void inOrderTraverse (Node localRoot)
if (localRoot != null)
inOrderTraverse(localRoot.leftChild);
localRoot.displayNode();
inOrderTraverse(localRoot.rightChild);
private int increment(int i)
return i++;
any help is greatly appreciated! thanks!

ok, thanks a lot!
so i was able to fix that, and it compiles, but when I run it, it gets stuck after i enter the name of the input and output files. anyone have any idea why it's doing that? I can't figure it out...
here's the edited code:
import java.io.*;
import java.util.*;
import java.util.StringTokenizer;
import java.lang.String.*;
class WordCount2
public static void main (String [] args) throws IOException
StringTokenizer tokenizer;
String inputpath, outputpath;
String line = "";
String str = "";
Tree tree = new Tree();
int i = 0;
int count = 0;
Node now = new Node();
BufferedReader stdin= new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the pathname of the input file: ");
inputpath = stdin.readLine();
System.out.println("Enter the pathname of the output file: ");
outputpath = stdin.readLine();
FileReader textFile1 = new FileReader(inputpath);
BufferedReader inputFile = new BufferedReader (textFile1);
FileWriter textFile2 = new FileWriter(outputpath);
PrintWriter outputFile = new PrintWriter(textFile2);
while ((line = inputFile.readLine()) != null)
tokenizer = new StringTokenizer(line, " ");
while (tokenizer.hasMoreTokens())
String s = tokenizer.nextToken().toLowerCase();
tree.insert(s, i);
tree.inOrderTraverse(now);
class Node
public String sData;
public int iData;
public Node leftChild;
public Node rightChild;
public Node()
sData = "";
iData = 0;
public void displayNode(String s, int i) throws IOException
String file = "test1.txt";
FileReader fr = new FileReader (file);
BufferedReader inFile = new BufferedReader(fr);
String line = inFile.readLine();
String file2 = "outfile.txt";
FileWriter fw = new FileWriter (file2);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter outFile = new PrintWriter(bw);
outFile.print (s);
outFile.print (" - ");
outFile.print (i);
outFile.flush();
class Tree
private Node root;
public Tree()
root = null;
public void insert(String sd, int id)
Node newNode = new Node();
newNode.sData = sd;
newNode.iData = id;
if (root == null)
root = newNode;
else
Node current = root;
Node parent;
while (true)
parent = current;
if ((newNode.sData).compareTo(current.sData) < 0)
current = current.leftChild;
if (current == null)
parent.leftChild = newNode;
return;
else if((newNode.sData).compareTo(current.sData) == 0)
increment(newNode.iData);
else
current = current.rightChild;
if(current == null)
parent.rightChild = newNode;
return;
public void inOrderTraverse (Node localRoot) throws IOException
String s = "";
int i = 0;
if (localRoot != null)
inOrderTraverse(localRoot.leftChild);
localRoot.displayNode(s, i);
inOrderTraverse(localRoot.rightChild);
private int increment(int i)
return i++;
thanks again!

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Message was edited by:
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Message was edited by:
since81
Message was edited by:
since81

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I am having problems figuring out how to do this.
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Every one likes to play games.
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        deepCopyRight(root.mRight, newRoot);
        return new Tree<T>(newRoot);
    }Its a similar recursive idea, but with 2 extra functions. I hope that helps. I don't have time right now to pinpoint the problem in your routine. Good luck.

Recover a Binary Tree

Ok people I need help!
I want to create, from a pre-order and in-order sequences, the post-order sequence! Obviously there are no repeated elements (characters from A to Z at this case).
The tree root it's the first character from pre-order and after that it's easy to take left and right sequences.
I found an interesting explanation: http://www.dcs.kcl.ac.uk/staff/pinz...st/html/l7.html
I've tried everything to make it recursive I think that's the best way to do it but somehow I can't make it work! My last code:
import java.io.*;
import java.util.*;
public class Problem
        static String readLn (int maxLg) // utility function to read from stdin
            byte lin[] = new byte [maxLg];
            int lg = 0, car = -1;
            try
                while (lg < maxLg)
                    car = System.in.read();
                    if ((car < 0) || (car == '\n')) break;
                    lin [lg++] += car;
            catch (IOException e)
                return (null);
            if ((car < 0) && (lg == 0)) return (null); // eof
            return (new String (lin, 0, lg));
        public static void main (String []args)
                for (int set = Integer.parseInt(readLn(10).trim()); set != 0; set--)
                        StringTokenizer tok = new StringTokenizer(readLn(100).trim()," ");
                        String preOrd = tok.nextToken();
                        String inOrd = tok.nextToken();
                        char root = preOrd.charAt(0);
                        BinaryNode tree = new BinaryNode(root);
                        // Left and right from inOrd
                        tok = new StringTokenizer(inOrd,Character.toString(root));
                        String inOrdLeft = tok.nextToken();
                        String inOrdRight = tok.nextToken();
                        // Take left and right from preOrd
                        String preOrdLeft = preOrd.substring(1,inOrdLeft.length()+1);
                        String preOrdRight = preOrd.substring(inOrdLeft.length()+1);
                        tree.left = work (preOrdLeft, 0, inOrdLeft);
                        tree.right = work (preOrdRight, 0, inOrdRight);
                        tree.printPostOrder();
                        System.out.println();
        public static BinaryNode work (String preOrd, int preOrdPoint, String inOrd)
                char    nodeChr = preOrd.charAt(preOrdPoint);
                String nodeStr = Character.toString(nodeChr);
                //System.out.println("Root: "+nodeStr+" preOrd: "+preOrd+" inOrd: "+inOrd);
                BinaryNode tempTree = new BinaryNode(nodeChr);
                StringTokenizer tok = new StringTokenizer(inOrd,nodeStr);
                try
                        String newInOrdLeft = tok.nextToken();
                        if (newInOrdLeft.length() == 1) { tempTree.left = new BinaryNode(newInOrdLeft.toCharArray()[0]); }
                        else if (newInOrdLeft.length() != 0) { tempTree.left = work(preOrd, preOrdPoint+1, newInOrdLeft); }
                catch (NoSuchElementException e) {}
                try
                        String newInOrdRight = tok.nextToken();
                        if (newInOrdRight.length() == 1) { tempTree.right = new BinaryNode(newInOrdRight.toCharArray()[0]); }
                        else if (newInOrdRight.length() != 0) { tempTree.right = work(preOrd, preOrdPoint+1, newInOrdRight); }
                catch (NoSuchElementException e) {}
                return tempTree;
class BinaryNode
        char chr;
        BinaryNode left = null;
        BinaryNode right = null;
        BinaryNode()
        BinaryNode(char c)
                this(c, null, null);
        BinaryNode(char c, BinaryNode lt, BinaryNode rt)
                chr = c;
                left = lt;
                right = rt;
        static int size(BinaryNode t)
                if (t == null) { return 0; }
                else { return size(t.left) + 1 + size(t.right); }
        static int height(BinaryNode t)
                if (t == null) { return 0; }
                else { return 1 + Math.max(BinaryNode.height(t.left), BinaryNode.height(t.right)); }
        void printPostOrder () {
                if( left != null )
                        left.printPostOrder( ); // Left
                if( right != null )
                        right.printPostOrder( ); // Right
                System.out.print(chr); // Node
        static BinaryNode insert (char c, BinaryNode t)
                Character tmp = new Character(c);
                if (t == null)
                        t = new BinaryNode(c, null, null);
                else if (tmp.compareTo(new Character(t.chr)) < 0)
                        t.left = insert(c, t.left );
                else if (tmp.compareTo(new Character(t.chr)) > 0)
                        t.right = insert(c, t.right);
                return t;
}

I don't know if this is a translation of your C code, but it can reconstruct any binary tree (with letters as nodes and no duplicates) from preorder and inorder traversals. Hope it helps.
import java.util.*;
public class ReconstructTree {
    public ReconstructTree() {
    public static void main(String[] args)
        String preorder = "ABDGKLRVWSXCEHMNFIOTUJPYQZ";
        String inorder = "KGVRWLSXDBAMHNECTOUIFPYJZQ";
        Map table = new HashMap();
        Map table2 = new HashMap();
        for(int i=0; i<inorder.length(); i++)
            table.put("" + inorder.charAt(i), new Integer(i));
            table2.put(new Integer(i), "" + inorder.charAt(i));
        List temppreorder = new ArrayList();
        for(int i=0; i<preorder.length(); i++)
            temppreorder.add(table.get("" + preorder.charAt(i)));
        Node root = constructTree(temppreorder);
        printPostOrder(root, table2);
    public static void printPostOrder(Node root, Map table)
        if(root == null)
            return;
        Node left = root.getLeft();
        Node right = root.getRight();
        printPostOrder(left, table);
        printPostOrder(right, table);
        System.out.print(table.get(new Integer(Integer.parseInt("" + root.getValue()))));
    public static Node constructTree(List preorder)
        Iterator it = preorder.iterator();
        int r = ((Integer)it.next()).intValue();
        Node root = new Node(r);
        Node node = root;
        while(it.hasNext())
            node = root;
            int a = ((Integer)it.next()).intValue();
            while(true)
                r = node.getValue();
                if(a < r)
                    if(node.getLeft() == null)
                        node.setLeft(new Node(a));
                        break;
                    else
                        node = node.getLeft();
                else
                    if(node.getRight() == null)
                        node.setRight(new Node(a));
                        break;
                    else
                        node = node.getRight();
        return root;
    public static class Node
        private Node left = null;
        private Node right = null;
        private int value;
        public Node(int v)
            value = v;
        public int getValue()
            return value;
        public Node getLeft()
            return left;
        public Node getRight()
            return right;
        public void setLeft(Node l)
            left = l;
        public void setRight(Node r)
            right = r;
}

Emptying a Binary Tree

Hello,
The problem I'm having is how to empty a binary tree. Here is my code for MyBinaryTree:
public class MyBinaryTree implements BinaryTree {
   private BinaryTreeNode root;
   protected static int numNodes;
   private static String tree = "";
    * Constructor that creates a binary tree with a root.
    * @param r The root node
    * @param num The number of nodes
   public MyBinaryTree(BinaryTreeNode r, int num) {
      root = r;
      numNodes = num;
    * Method to make the binary tree empty.
   public void makeEmpty() {
      root.left = null;
      root.right = null;
      root = new BinaryTreeNode(null,null,null,null,null);
      numNodes = 0;
    * Method to make a root with key k and element el.
    * @param k The key of the root
    * @param el The element in the root
   public void makeRoot(Comparable k, Object el) {
      root = new BinaryTreeNode(k,el);
      numNodes++;
    * Method to return the root of the binary tree.
    * @return The root of the tree
   public BinaryTreeNode root() {
      return root;
    * Method to return the left child of a node.
    * @param node The node whose left child is wanted.
    * @return The left child of the node
    * @see NoNodeException
   public BinaryTreeNode leftChild(BinaryTreeNode node) throws NoNodeException {
      if (node.left == null) throw new NoNodeException("No left child!");
      else return node.leftChild();
    * Method to set the left child of node "node".
    * @param node The node to be given a left child
    * @param child The node to be set as left child
   public void setLeftChild(BinaryTreeNode node, BinaryTreeNode child) {
      node.setLeftChild(child);
      numNodes++;
    * Method to return the right child of a node.
    * @param node The node whose right child is wanted.
    * @return The right child of the node
    * @see NoNodeException
   public BinaryTreeNode rightChild(BinaryTreeNode node) throws NoNodeException{
      if (node.right == null) throw new NoNodeException("No right child!");
      else return node.rightChild();
    * Method to set the right child of node "node".
    * @param node The node to be given a right child
    * @param child The node to be set as right child
   public void setRightChild(BinaryTreeNode node, BinaryTreeNode child) {
      node.setRightChild(child);
      numNodes++;
    * Method to return the parent of a node.
    * @param node The node whose parent is wanted.
    * @return The parent of the node
    * @see NoNodeException
   public BinaryTreeNode parent(BinaryTreeNode node) throws NoNodeException {
      if (node.p == null) throw new NoNodeException("No parent!");
      else return node.parent();
    * Method to set the parent of node "node".
    * @param node The node to be given a parent
    * @param pt The node to be set as parent
   public void setparent(BinaryTreeNode node, BinaryTreeNode pt) {
      node.setParent(pt);
      numNodes++;
    * Method to return the key of the specified node.
    * @param node The node with the key to be returned
    * @return The key of the node
   public Comparable getKey(BinaryTreeNode node) {
      return node.getKey();
    * Method to set the key of the specified node.
    * @param node The node for which the key will be set.
    * @param k The key to be set.
   public void setKey(BinaryTreeNode node, Comparable k) {
      node.setKey(k);
    * Method to get the element in the specified node.
    * @param node The node with the element to be returned.
    * @return The element in the node.
   public Object getElement(BinaryTreeNode node) {
      return node.getElement();
    * Method to put an element into the specified node.
    * @param node The node that will have an element put in it.
    * @param o The element to be inserted.
   public void setElement(BinaryTreeNode node, Object o) {
      node.setElement(o);
    * Method to add a left child to the specified node.
    * @param theNode The node that the left child will be added to.
    * @param k The key associated with the left child.
    * @param el The element in the left child.
   public void addLeftChild (BinaryTreeNode theNode, Comparable k, Object el) {
      BinaryTreeNode temp = new BinaryTreeNode(k,el);
      temp.setParent(theNode);
      theNode.setLeftChild(temp);
      numNodes++;
    * Method to add a right child to the specified node.
    * @param theNode The node that the right child will be added to.
    * @param k The key associated with the right child.
    * @param el The element in the right child.
   public void addRightChild (BinaryTreeNode theNode, Comparable k, Object el) {
      BinaryTreeNode temp = new BinaryTreeNode(k,el);
      temp.setParent(theNode);
      theNode.setRightChild(temp);
      numNodes++;
    * Method to remove the left child of the specified node.
    * @param theNode The node which the left child will be removed.
   public void removeLeftChild(BinaryTreeNode theNode) {
      ((BinaryTreeNode)(theNode.left)).p = null;
      theNode.left = null;
      numNodes--;
    * Method to remove the right child of the specified node.
    * @param theNode The node which the right child will be removed.
   public void removeRightChild(BinaryTreeNode theNode) {
      ((BinaryTreeNode)(theNode.right)).p = null;
      theNode.right = null;
      numNodes--;
    * Private method to perform an inorder traversal on the tree.
    * @param t A MyBinaryTree object
    * @param n The starting node.
   private static String inorderPrint(MyBinaryTree t, BinaryTreeNode n) {
      String spaces = "";
      for (int i = 0; i < (numNodes - 1)/2; i++) spaces += " ";
      if (n.left != null || n.right != null) inorderPrint(t,t.leftChild(n));
      tree += spaces + n.getElement();
      if (n.left != null || n.right != null) inorderPrint(t,t.rightChild(n));
      return tree;
    * Private method to perform an inorder traversal on the tree.
    * @param t A MyBinaryTree object
    * @param n The starting node.
    * @param pos The current position in the tree.
    * @return A tree with an asterix beside the current position
   private static String inorderPrint2(MyBinaryTree t, BinaryTreeNode n,
                                       BinaryTreeNode pos) {
      String spaces = "";
      for (int i = 0; i < (numNodes - 1)/2; i++) spaces += " ";
      if (n.left != null || n.right != null) inorderPrint2(t,t.leftChild(n),pos);
      if (n.getElement() == pos.getElement()) tree += spaces + n.getElement() + "*";
      else tree += spaces + n.getElement();
      if (n.left != null || n.right != null) inorderPrint2(t,t.rightChild(n),pos);
      return tree;
    * Method to return a String representation of the binary tree.
    * @return String representation of the binary tree
   public String toString() {
      if (root.getElement() == null) return "*** Tree is empty ***";
      else {
         MyBinaryTree temp = new MyBinaryTree(root,numNodes);
         return inorderPrint(temp,root);
    * Method to return a String of the binary tree with an asterix beside the
    * current position.
    * @param currentPosition The current position.
    * @return A String of the tree with an asterix by the current position
   public String toString(BinaryTreeNode currentPosition) {
      if (root.getElement() == null) return "*** Tree is empty ***";
      else {
         MyBinaryTree temp = new MyBinaryTree(root,numNodes);
         return inorderPrint2(temp,root,currentPosition);
}Those are all the methods I'm allowed to have. When I run makeEmpty, it seems to work, but then if I do makeRoot, the old tree prints again. It's quite bizarre. Any tips on how to empty the tree correctly?

Here is the BinaryTreeNode code.
public class BinaryTreeNode {
    // Instance variables (Note: they are all "private")
    protected Comparable key;           // The key at this node
    protected Object element;          // The data at this node
    protected BinaryTreeNode left;     // Left child
    protected BinaryTreeNode right;    // Right child
    protected BinaryTreeNode p;        // The Parent
    // Constructors
    BinaryTreeNode( Comparable theKey, Object theElement, BinaryTreeNode lt,
                    BinaryTreeNode rt, BinaryTreeNode pt ) {
        key      = theKey;
        element = theElement;
        left     = lt;
        right    = rt;
        p        = pt;
    BinaryTreeNode( Comparable theKey, Object theElement) {
        key      = theKey;
        element = theElement;
        left     = null;
        right    = null;
        p        = null;
    // return the key attached to this node
    public Comparable getKey() {
        return key;
    // set the key attached to this node to be Comparable k
    public void setKey(Comparable k) {
        key = k;
    // return the element attached to this node
    public Object getElement() {
        return element;
    // set the element attached to this node to be Object o
    public void setElement(Object o) {
        element = o;
    // return left child
    public BinaryTreeNode leftChild() {
        return left;
    // set left child to be node n
    public void setLeftChild(BinaryTreeNode n) {
        left = n;
    // return right child
    public BinaryTreeNode rightChild() {
        return right;
    // set right child to be node n
    public void setRightChild(BinaryTreeNode n) {
        right = n;
    // return parent
    public BinaryTreeNode parent() {
        return p;
    // set parent to be node n
    public void setParent(BinaryTreeNode n) {
        p = n;
}

Binary tree problems.

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