import java.io.*; 
import java.util.*;
import javax.swing.JOptionPane;

public class Train {
  
  public FileReader file;
  public StreamTokenizer st;
  public HashMap counts = new HashMap();
  public Hashtable cword;
  
/** Creates a new instance of train */
public Train() {
    
    String fileName = "SPAM.txt";     
    String data;    
    HashMap counts = new HashMap(); 
    int tokenType = 0;
    int numberOfTokens = 0;
    
    try 
    {      
    FileReader file = new FileReader(fileName);
    StreamTokenizer st = new StreamTokenizer(new BufferedReader(file));
    
    st.ordinaryChar('!');
    st.ordinaryChar('$');
    st.ordinaryChar('"');
    st.whitespaceChars('/','/');
    st.whitespaceChars('\\','\\');
    st.whitespaceChars('.','.');
    st.whitespaceChars(',',',');
    st.whitespaceChars(';',';');
    st.whitespaceChars(':',':');
    st.whitespaceChars('=','=');
    st.whitespaceChars('\'','\'');
    st.whitespaceChars('`','`');
    st.whitespaceChars('[',']');   
    
   while(st.nextToken() != StreamTokenizer.TT_EOF) {
     
    String s;
    
    switch(st.ttype) {
     case StreamTokenizer.TT_EOL:
      s = new String("EOL");      
      break;
      
    /** case StreamTokenizer.TT_NUMBER:
      s = Double.toString(st.nval);      
      break;**/
      
     case StreamTokenizer.TT_WORD:
      s = st.sval; // Already a String
      
     // System.out.println("Token Extracted = " + st.sval);
      st.lowerCaseMode(true);
      numberOfTokens++;
      break;
      
     default: 
      s = String.valueOf((char)st.ttype);
      
    }
    
    if(counts.containsKey(s))
     ((Counter)counts.get(s)).increment();
    else
     counts.put(s, new Counter());
   }
    }   
  catch(IOException e) 
  {
   System.out.println("st.nextToken() unsuccessful");
   System.out.println("Problem reading " + fileName );
   System.out.println("Exception: " + e);
   e.printStackTrace();
  }
    //create instance of commonwords
    CommonWords c = new CommonWords();    
    cword = c.cwords; 
    
    //remove the commonwords from HashMap
    counts.remove(cword);
    System.out.println("File "+fileName+" was succesfully loaded and Stored.");
    System.out.println("Tokens in File :" + numberOfTokens);
    System.out.println(cword);    
   }

public static void main(String[] args) 
 {
   Train t = new Train();  
 }  
}

import java.io.*; 
import java.util.*;
import javax.swing.JOptionPane;

public class CommonWords 
{  
  public Hashtable cwords;
  public FileReader file;
  public StreamTokenizer st;
  
public CommonWords() {     
    
    String fileName = "cwords.txt";     
    int tokenType = 0;
    int numberOfTokens = 0; 
    
   try
   {
     Reader cWords = new BufferedReader(new FileReader(fileName));      
     StreamTokenizer stc = new StreamTokenizer(cWords); 
     
     int i=0; 

     while(stc.nextToken() != StreamTokenizer.TT_EOF)
     {
       cwords.put(stc.sval.toLowerCase(), new Integer(i));       
       System.out.println("Token Extracted = " + stc.sval);        
       i=i++;
     }
   }
    catch(IOException e) 
      {
       System.out.println("st.nextToken() unsuccessful");
       System.out.println("Problem reading " + fileName );
       System.out.println("Exception: " + e);
       e.printStackTrace();
      }    
  } 
}

java.lang.NullPointerException
    at CommonWords.<init>(CommonWords.java:26)
    at Train.<init>(Train.java:80)
    at Train.main(Train.java:92)
Exception in thread "main"