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In Topic: BinarySearchTree - Search Method Works but Fails to Print Result

Posted 21 Apr 2013

That does make sense to me, so I've added it. And while I did learn something...it still doesn't solve my searchFor method problem, not returning the value it has found.
In Topic: BinarySearchTree - Search Method Works but Fails to Print Result

Posted 21 Apr 2013

macosxnerd101, on 21 April 2013 - 08:39 PM, said:
Quote
Where should I extend comparable? I do that already for the class data type which the Node is holding.

Your BinarySearchTree class, and you aren't doing it for Node.

I am doing it for the class Word though, where I really want the compareTo method to come into play. Or should I change that?

In Topic: BinarySearchTree - Search Method Works but Fails to Print Result

Posted 21 Apr 2013

macosxnerd101, on 21 April 2013 - 08:24 PM, said:

Also, a note on your design. Your BST should be defined so that T extends Comparable<? super T> in your class definition. You shouldn't be casting T to Word in your search() method. You should be able to invoke compareTo() directly.

I have a bad habit when working with generics to just cast my method for the current program I'm using just to make it easier on myself. Where should I extend comparable? I do that already for the class data type which the Node is holding.

And for a runnable sample here is the code of all the classes that I'm using and a simple main class that tests the search method.

public class Node<T>
{
    private T data;
    private Node left;
    private Node right;


    public Node (T newData)
    {
        data = newData;
        left = null;
        right = null;
    }

    public Node ()
    {
        data = null;
        left = null;
        right = null;
    }

    public String toString ()
    {
    
    		String s = data.toString();
    		if (left != null ) {
    			s += "\n" + left.toString();
    		} 
    		if (right != null) {
    			s+= "\n"+ right.toString();
    		}
    		
    		
    		return s;
    		


    }

    public void setData (T newData)
    {
        data = newData;
    }

    public T getData ()
    {
        return data;
    }

    public void setLeft (Node newLeft)
    {
        left = newLeft;
    }

    public Node getLeft ()
    {
        return left;
    }

    public void setRight (Node newRight)
    {
        right = newRight;
    }

    public Node getRight ()
    {
        return right;
    }

    public boolean equals (Node theOther)
    {
        return this.data.equals (theOther.data);
    }

  public int compareTo (Node theOther)
    {
        return ((Word) this.getData()).compareTo((Word) theOther.getData());
    }



}

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author fsylin
 */
public class BinaryTree<T>
{
    private Node<T>  root ;

    public BinaryTree ()
    {
        root = null;
    }

    public void inOrder (Node root)
    {
        if (root != null)
        {
            inOrder (root.getLeft ());
            System.out.println (root);
            inOrder (root.getRight ());
        }
    }

    public void preOrder (Node root)
    {
        if (root != null)
        {
            System.out.println (root);
            preOrder (root.getLeft ());
            preOrder (root.getRight ());
        }
    }

    public void postOrder (Node root)
    {
        if (root != null)
        {
            postOrder (root.getLeft ());
            postOrder (root.getRight ());
            System.out.println (root);
        }
    }

    public boolean empty ()
    {
        return (root == null);
    }

    public Node getRoot ()
    {
        return root;
    }

    public void setRoot (Node newRoot)
    {
        root = newRoot;
    }




}

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author fsylin
 */
public class BinarySearchTree<T>  extends BinaryTree<T>
{
    public BinarySearchTree ()
    {
        super ();
    }

    public Node add(T element, Node<T> root) {
    	if(root == null) 
    		root = new Node(element);
    	else if(((Word) element).compareTo((Word)root.getData()) <= 0)
    		root.setLeft(add(element, root.getLeft()));
    	else
    		root.setRight(add(element, root.getRight()));
    	
    	return root;
    		
    }
    
    public String search(T element, Node<T> root) {
    	if(root == null) 
    		return null;
    	else if(((Word) element).compareTo((Word)root.getData()) < 0)
    		return search(element, root.getLeft());
    	else if(((Word) element).compareTo((Word) root.getData()) > 0)
    		return search(element, root.getRight());
    	else 
    		return root.toString();
    }
    
    public boolean addOne (T newMember)
    {
        boolean success = true;
        Node<T> newNode = new Node<T> (newMember);
        if (empty ())
            setRoot (newNode);
        else
        {
            Node p = null;
            Node c = getRoot ();
            int compare = 0;

            while (c != null)
            {
                compare = newNode.compareTo (c);
                if (compare == 0)
                {
                    System.out.println ("duplicate found");
                    success = false;
                    return success;
                }
                else
                {
                    p = c;
                    if (compare > 0)
                        c = c.getRight ();
                    else
                        c = c.getLeft ();
                }
            }

            if (compare > 0)
                p.setRight (newNode);
            else
                p.setLeft (newNode);
        }
        return success;

    }

   public T delete (Node key)
    {
       T dataInDeleted = null;
       if (!empty ())
       {
           Node p = null;
           Node c = getRoot ();
           int compare = 0;

            while (c != null)
            {
                compare = key.compareTo (c);
                if (compare == 0)
                    break;
                else
                {
                    p = c;
                    if (compare > 0)
                        c = c.getRight ();
                    else
                        c = c.getLeft ();
                }
            }

           if (c == null)
           {
               System.out.println  ("not found");
               return dataInDeleted;
           }
           else
           {
               dataInDeleted = (T) c.getData ();
               Node betweenPnC  = null;

               // covers left and one-child cases
               if (c == getRoot ())
                   betweenPnC = getRoot ();
               else if (c == p.getLeft ())
                   betweenPnC = p.getLeft ();
               else
                   betweenPnC = p.getRight ();

               if (betweenPnC.getRight () == null)
                   betweenPnC = betweenPnC.getLeft ();
               else if (betweenPnC.getLeft () == null)
                   betweenPnC = betweenPnC.getRight ();
               //end of leaf and one-child cases

               //2-child case, go right once then keep going left till null
               Node px = c;
               Node pc = c.getRight ();
               while (pc.getLeft () != null)
               {
                   px = pc;
                   pc = pc.getLeft ();
               }

               c.setData ((T) pc.getData ());

               if (px == c)
                   px.setRight (pc.getRight ());
               else
                   px.setLeft (pc.getRight ());
           }

      }

     return dataInDeleted;



   }

   //use inorder traversal
   public void traverse ()
    {
        Node startPoint = getRoot ();
        inOrder (startPoint);


    }

    public Node binarySearch (Node key)
    {
		Node found = null;
		Node temp = getRoot ( );
		while (temp != null)
		{
				int x = key.compareTo (temp);
				if (x == 0)
				{
					found = temp;
					break;
				}
				else if (x < 0)
					temp = temp.getLeft ( );
				else
					temp = temp.getRight ( );
		}

		return found;
	}





}

public class Word implements Comparable<Word> {
	
	String name = "";
	String define = "";
	
	public Word(String newName) {
		name = newName;
		define = "No current definition yet...";
	}
	public Word(String newName, String newDef) {
		name = newName;
		define = newDef;
	}
	
	public Word() {}

	public String name() {
		return name;
	}
	
	public String define() {
		return define;
	}
	
	
	public int compareTo(Word otherWord) {
		int comparison = name.compareToIgnoreCase(otherWord.name());
			if(comparison < 0) 
				comparison = -1;
			else if(comparison > 0) 
				comparison = 1;
			else if(comparison ==0)
				comparison = 0;
			
		return comparison;
	}

	public String toString() {
		String output = "";
		output = name + ": " + define;
		return output;
	}
}

Ignore the second constructor

import java.util.ArrayList;
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
public class Dictionary {
		
	Scanner input = null;
		Scanner scan = new Scanner(System.in);
		ArrayList<Word> list = new ArrayList<Word>();
		BinarySearchTree<Word> wordTree = new BinarySearchTree<Word>();
		
	public Dictionary(Word[] newList) {
		for(int i = 0; i < newList.length; i++) {
			list.add(newList[i]);
		}
		
		for(int x = 0; x < list.size(); x++)
			wordTree.addOne(list.get(x));
	}
	
/*	
	public Dictionary() {
		
		boolean fileOk = true;
		do {
			fileOk = true;
			System.out.println("Enter source file name: ");
			String sourceFileName = scan.next();
			try
			{
				input =  new Scanner (new File (sourceFileName));
			}
			catch (FileNotFoundException ex)
			{
				System.out.println ("Failed to find file...");
				fileOk = false;
			}
		} while (!fileOk);
		
		while(input.hasNext()) {
		
			String aLine = input.nextLine ();
			int pos = aLine.indexOf(":");
			String name = aLine.substring(0,pos - 1);
			String definition = aLine.substring(pos + 1);
			
			Word newWord = new Word(name, definition);
			list.add(newWord);
			
		}

	}
	*/
	
	public String searchFor(Word searchedWord) {
		
		if(wordTree.search(searchedWord, wordTree.getRoot()) == null) {
			System.out.println("Word not found. Type in the word you want to add, press enter, and then type it's definition.");
			String name = scan.next();
			String def = scan.next();
			Word newWord = new Word(name, def);
			wordTree.add(newWord, wordTree.getRoot());
		}
			
		return wordTree.search(searchedWord, wordTree.getRoot());
		
	}
	
	public String toString() {
		return wordTree.getRoot().toString();
	}

}

import java.util.*;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		Scanner scan = new Scanner(System.in);
		
		Word GUI = new Word("GUI", "Graphical User Interface");
		Word Mouse = new Word("Mouse","Accesory that allows simpler interface with a GUI");
		Word RAM = new Word("RAM","Random Accesss Memory");
		Word CLI = new Word("CLI","Command Line Interface");
		Word AI = new Word("AI","Artifical Intelligence");
		Word IDE = new Word("IDE","Intergrated Development Enviornment");
		
		Word[] list = new Word[]{GUI, Mouse, RAM, CLI, AI, IDE};
		
		Dictionary computerDefs = new Dictionary(list);
		System.out.println(computerDefs);
		System.out.println("\nWhat word would you like to search for?");
		String x = scan.next();
		Word wordN = new Word(x);
		computerDefs.searchFor(wordN);
		
	}

}

That might not be what you were looking for when you said minimally runnable lol....but the BST class itself takes two other classes to run so I figure I might as well post the exact thing giving me the error.

In Topic: NullPointerException when enQueueing User Created Queue Class

Posted 14 Apr 2013
pbl, on 14 April 2013 - 09:53 PM, said:
this is ridiculous
```
           for(i = 0; i < capacity; i++) 
               ++count;
```
simply write: count = capacity;
I'm using the do-while loop there to break out of the for loop when the next space is "null". That way, if 5 objects are in the array, but the capacity is still 25, it will stop the count at 5 and return that number; thus giving me the "length" being the actual amount of objects in the array. I hope that makes sense because when I wrote it, it seemed like it would have worked for it's purpose at the time. It was an old method I created which I ended up not using.

Would you happen to know if there is anything wrong with my dequeue method? I'm having more trouble later on...might need a new topic but everytime I try to dequeue an object out of the array it doesn't seem to actually do it for some reason...
In Topic: NullPointerException when enQueueing User Created Queue Class

Posted 14 Apr 2013

Ok, so I cleared my head and ran through the debugger one more time.

In my constructor (out of bad habits developed in an earlier class) I had decided to make the Queue that was being used set to null. I have deleted that and moved on and I think I am in the clear now.

Thanks for reading!