Hashtable Comparison Algorithm

[danieldrave]

Hi all,

 

Involved in many projects at the moment & I've had a mental block with this algorithm.

 

Here's the source code, I'm trying to compare the keys in my Hashtable and the values in the array and if the "words" appear in both data structures to produce a result, but the line for line algorithm is really messing with my head:

 

public void addBook(String filename) throws IOException

 

{

 

String[] linearray;

 

String line;

 

try

 

{

 

File b = new File(filename);

 

BufferedReader fileread = new BufferedReader(new FileReader(b));

 

in = new Scanner(b);

 

 

 

while(in.hasNextLine())

 

{

 

line = fileread.readLine(); /* Read in whatever line */

 

linearray = line.split("([.,!?:;'\"-]|\\s)+)"); /* this handles punctuation and whitespace and adds it to the array */

 

for(int i=0; i<=linearray.length; i++)

 

{

 

 

 

}

 

}

 

}

 

 

 

catch (FileNotFoundException e)

 

{

 

e.printStackTrace();

 

}

 

}

 

 

 

 

Any help you could provide would be great, I'm not looking for spoon fed source code, just some algorithms to help get my creative juices flowing!

 

 

 

 

Dan xx

 

 

[alextui]

for(int i=0; i<=linearray.length; i++){

// get word from array at first

String word = linearray;

//then use word to query the hashtable

Object o = targetHashTable.get(word);

//if the result is not null, it means there is a hit.

if(o!=null){

//product the result

}

}

Edited October 25, 2011 by alextui

[danieldrave]

Thanks very much that really did help solve my problem!

 

Marvellous xxx

[danieldrave]

I'm getting a null pointer exception at the line with Object o on it :/

 

However I think it may be an error in my main method.. here's the source code but I'm not sure because all I'm doing is calling a method from the HashTable class & I have initialised that at the first line of the method.

 

package cs21120_assignment_data;

 

 

 

 

import java.io.*;

 

import java.util.Hashtable;

 

import java.util.Scanner;

 

 

 

 

import javax.swing.SwingUtilities;

 

 

 

 

public class Concordance {

 

 

 

 

/**

 

* @param args

 

* @throws IOException

 

*/

 

public static void main(String[] args) throws IOException

 

{

 

 

 

HashTable hashtable = new HashTable ();

 

 

 

hashtable.addBook("oliver.txt");

 

 

 

hashtable.readSourceFile("index.txt");

 

 

 

}

 

 

 

}

 

 

 

 

The source code for the HashTable is the same as above, but I'm not convinced it's a problem with main method even after reading the error message...

 

 

 

 

Exception in thread "main" java.lang.NullPointerException

 

at cs21120_assignment_data.HashTable.addBook(HashTable.java:86)

 

at cs21120_assignment_data.Concordance.main(Concordance.java:26)

 

 

 

 

 

 

 

 

 

 

 

[khaled]

I don't know about your code, but I've built several optimal structures on Java as a library ...

 

They're in my blog .. Check them: Blog:Java

 

The first is optimal binary tree which is a hash structure of binary trees with O(log(N/K)), Blog:OBT

 

The second is Insta:Associative Array which is an associative array with O(1), Blog:Insta

 

good luck

Edited November 14, 2011 by khaled