Hashing with double linked list....

Question

Okay, everything compiles great but I'm getting a NullPointerException upon running the program.
'line' is a string from a file to let you know that much. 'firstnode', 'nownode', and 'lastnode' are pointers in my array linked list 'anArray'. I know clever names. lol But hey, my professor uses variable names like 'X' 'T' and 'G' all the time, confusing bastard. :-) Anywho... I put a note in the code so you can see where this exception is taking place. Any help is 100% welcomed and appreciated!
     while( line != null )
     int hashindex = hash(line, 20);
     if(firstnode[hashindex] == null)
             firstnode[hashindex] = nownode[hashindex] = lastnode[hashindex] = new ListNode( line );
     else
             nownode[hashindex] = new ListNode( line );
//This line is the exception, if I comment it out, the next line throws it
          anArray[hashindex].CONS(nownode[hashindex], lastnode[hashindex]);
          anArray[hashindex].LCONS(lastnode[hashindex], nownode[hashindex]);
//If I comment out the 2 lines above this line DOES NOT throw an exception, weird
          lastnode[hashindex] = nownode[hashindex];
     line = input.readLine();
     }

Answer 1

Okay, here's some more code... Just the top portion of the program. Keep in mind that methods like CONS, LCONS, CDR, and LCDR are just using the ListNode methods such as .ptr and stuff... My professor makes us use this ADT he provided. I can post ALL code if you would like but I dont think all that is necessary.
static BufferedReader input, console;
static List hashtable = new List();
static List[] anArray = new List[20];
static ListNode[] nownode, firstnode, lastnode;
static String message = "";
static int nodecount = 0;
public static void openFile()
//Opens the file for input and throws and exception if the file is not there
     File taskFile = new File("prices.txt");
     try
         input = new BufferedReader(new FileReader( taskFile ));
     catch( FileNotFoundException fileNotFoundException )
     outputStuff("Error", "The file does not exist!", "error");
public synchronized static void setupTable() throws IOException
     firstnode = new ListNode[20];
     nownode = new ListNode[20];
     lastnode = new ListNode[20];
     String line = input.readLine();
     firstnode[0] = nownode[0] = lastnode[0] = new ListNode( line );
     while( line != null )
     hashindex = hash(line, 20);
     if(firstnode[hashindex] == null)
             firstnode[hashindex] = nownode[hashindex] = lastnode[hashindex] = new ListNode( line );
     else
             nownode[hashindex] = new ListNode( line );
          anArray[hashindex].CONS(nownode[hashindex], lastnode[hashindex]);
          anArray[hashindex].LCONS(lastnode[hashindex], nownode[hashindex]);
          lastnode[hashindex] = nownode[hashindex];
     line = input.readLine();
     for(int i = 0; i <= 20; i++)
          while( nownode[i] != null)
          message += "String = " + anArray.info( nownode[i], 0 ) + "\tIndex = " + i + "\n";
     nownode[i] = anArray[i].CDR(nownode[i]);
     outputStuff("test", message, "blah");
}//End setupTable