Thread: Implementing a binary search tree using recursion?

Hello everyone,

I am trying to implement this binary search tree using recursion.

On the first iteration of the loop within the driver class, the first record gets added as root just as I expected, but now on the second iteration within the driver class the root is overwritten with the second record before it even steps in to the insert method. Why is this happening?

Here is my code:

Main Driver Class:

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class GolfCourseDriver {
 
	public static void main(String[] args) throws IOException {
 
		FileInputStream fstream = new FileInputStream("GolfCourseData.txt");
		DataInputStream in = new DataInputStream(fstream);
		BufferedReader br = new BufferedReader(new InputStreamReader(in));
		Tree searchTree = new Tree();
		GolfCourse gcRec = new GolfCourse();
		String strLine;
		int count = 1;
		String totalRecs = br.readLine();  // get total num of records
 
		// build each node from each golfCourseObject
		while((strLine = br.readLine()) != null){
 
			switch(count){			
			case 1:  gcRec.setCourseName(strLine); break;
			case 2:  gcRec.setLocation(strLine); break;
			case 3:  gcRec.setGreensFee(Double.valueOf(strLine)); break;
			case 4:  gcRec.setPar(Integer.valueOf(strLine)); break;
			case 5:  gcRec.setDesigner(strLine); break;
			case 6:  gcRec.setYearBuilt(Integer.valueOf(strLine)); break;
			case 7:  gcRec.setYards(Integer.valueOf(strLine)); break;			
			default: System.out.println("Error! invalid item found."); break;		
			}
			// reset count 
			if(count == 7){
				searchTree.insert(gcRec);
				count = 1;
			}
			else{
				count++;
			}
		}	
		in.close();
  }
}

Tree Class

public class Tree {
 
  private TreeNode root;
 
  public Tree() {
    root = null;
  }
 
  public void insert(GolfCourse object) {
	root = insert(object, root);
  }
 
  private TreeNode insert(GolfCourse newObject, TreeNode  node) {
	if (node == null) {
	    return new TreeNode(newObject);
	}
	if (newObject.greensFee == node.object.greensFee) {
	    // replace the value in this node with a new value
	    node.object = newObject;
	    // alternative code creates new node, leaves old node unchanged:
	    //return new BinaryNode<T>(value, node.left, node.right);
	} else {
	    if (newObject.greensFee < node.object.greensFee) {	// add to left subtree
		node.lPtr = insert(newObject, node.lPtr);
	    } else {		// add to right subtree
		node.rPtr = insert(newObject, node.rPtr);
	    }
	}
	return node;
  }
}

Tree Node Class:

public class TreeNode {
 
	GolfCourse object;
	TreeNode lPtr;
	TreeNode rPtr;
 
	public TreeNode() {
	}
 
	public TreeNode(GolfCourse data){
	object = data;
	}
}

First few records of text Data passed in "GolfCourseData.txt:

22
Abacoa Golf Club
Jupiter
45
72
Joe Lee
1999
7200
Eastpointe Country Club
PB Gardens
50
72
George and Tom Fazio
1974
6890

Thanks

Originally Posted by copeg

You are inserting the same object at each position. First you insert the object as the root, then when you read the next values change the values of that same object. Create new instances of your user data object to prevent overwriting of previous


And please be forthright when cross-posting

This thread has been cross posted here:

http://www.java-forums.org/new-java/57812-implementing-binary-search-tree.html

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Sorry about the cross posting, this was driving me crazy. Anyways, I appreciate the help you were right. I created a new instance after each insert in the driver class and it worked. Again, thanks for the information.