Re: Print a binary search tree

On Oct 24, 7:29 pm, Roedy Green <see_webs...@mindprod.com.invalid>
wrote:


I have fixed the print to console problem. Now I am having problems
printing to the text file. I've commented in the file where the
problem is. Any help is greatly appreciated.

// Kevin Altizer 23 October 2007
// PURPOSE: File for a binary search tree class
// COMPILER: Java JDK 1.5, with jGRASP 1.8.6_04 as the IDE
// LIMITATIONS: Limited error checking

import java.util.*;
import java.io.*;

class AltizerProject4 implements Serializable {

   // Inner class defining a binary tree node
   private class TreeNode {
      private TreeNode left;
      private Comparable key;
      private TreeNode right;
   }

   // Instance variables
   private TreeNode root, parent, child;
    private String sourceName = null;

   // Constructor
   public AltizerProject4() {
      root = null;
   }

   // Inserts a key into the set
   public void insert(Comparable key) {
      TreeNode newNode;
      if (search(key)) {
            System.out.println("Duplicates are not allowed");
        }

        else {
         newNode = new TreeNode();
         newNode.key = key;
         newNode.left = null;
         newNode.right = null;
            if (parent == null)
               root = newNode;
            else if (parent.key.compareTo(key) > 0)
               parent.left = newNode;
            else
               parent.right = newNode;
               }
      }

   // Removes a key from the set
   public void remove(Comparable key) {
      if (!search(key)) {
            System.out.println(key + " is not in the database");
        }

        else {
         if (child == root)
            root = deleteNode(root);
         else if (parent.left == child)
            parent.left = deleteNode(parent.left);
         else
            parent.right = deleteNode(parent.right);

        System.out.println("The name " + key + " was deleted");
      }
   }
   // Determines whether a key is in the set
   public boolean contains(Comparable key) {
      if (!search(key))
         return false;
      return true;
        }

   // Private method that searches for a key
   private boolean search(Comparable key) {
      parent = null;
      child = root;
      while (child != null)
      {
         if (child.key.equals(key))
            return true;
         parent = child;
         if (child.key.compareTo(key) > 0)
            child = child.left;
         else
            child = child.right;
      }
      return false;
   }

   // Private method that deletes a node
   private TreeNode deleteNode(TreeNode node) {
      TreeNode inorderSuccessor, successorsParent;

      if (node.right == null)
         return node.left; // 0-1 Child
      else if (node.left == null)
         return node.right; // 1 Child
      else { // 2 Children
         successorsParent = node.left;
         inorderSuccessor = successorsParent.right;
         if (inorderSuccessor == null) {
            node.left = successorsParent.left;
            node.key = successorsParent.key;
         }
           else {
            while (inorderSuccessor.right != null) {
               successorsParent = inorderSuccessor;
               inorderSuccessor = inorderSuccessor.right;
            }
            successorsParent.right = inorderSuccessor.left;
            node.key = inorderSuccessor.key;
         }
      }
   return node;
   }

    // print tree in order
   public void print() {
   recprint(root);
   System.out.println();
   }
   private void recprint(TreeNode p) { // recursively print the tree
values in sorted order
   if (p == null)
   return;
   recprint (p.left);
   System.out.print(p.key + "\n");
   recprint (p.right);
   }

    // load data from text file
    public void loadData(String sourceName) {
    // Remember the source name.
    this.sourceName = sourceName;
    try {
      // Create a BufferedReader for the file.
      BufferedReader in = new BufferedReader(
          new FileReader(sourceName));
      String name;

      // Read each name and number and add the entry to the list.
      while ( (name = in.readLine()) != null) {
        // Add an entry for this name and number.
        insert(name);
      }

      // Close the file.
      in.close();
    }
    catch (FileNotFoundException ex) {
      // Do nothing - no data to load.
      return;
    }
    catch (IOException ex) {
      System.err.println("Load of directory failed.");
      ex.printStackTrace();
      System.exit(1);
    }
  }

  // begin save method
   /** Method to save the directory.
      pre: The directory has been loaded with data.
      post: Contents of directory written back to the file in the
            form of name-number pairs on adjacent lines.
            modified is reset to false.
      */
    public void save(String sourceName) {
      try {
        // Create PrintWriter for the file.
        PrintWriter out = new PrintWriter(
            new FileWriter(sourceName));

          // Write the name(s) to the text file.
             // The next line is where the problem is.
             // For some reason I get a 'cannot fine symbol' error at
             // the selection period before print();
             out.print();

        // Close the file.
        out.close();
      }
      catch (Exception ex) {
        System.err.println("Save of directory failed");
        ex.printStackTrace();
        System.exit(1);
      }
    }

} // end class