Generics problem - unchecked and unsafe problems

Question

basically my teacher said it needs to run if she types in "% javac *.java " otherwise i'll get a zero...
so with that said, i've read that to fix the generic problem you can do the -Xlint:unchecked but that wont help me.
and i've also read about raw types being the source of the problem, but now i'm completely stuck as to how to fix it. any suggestions would be greatly appreciated.
here is my source code for the file that is causing this:
import java.io.*;
import java.util.*;
public class OrderedLinkedList<T> implements OrderedListADT<T>
     private int size;
     private DoubleNode<T> current;
     public OrderedLinkedList()
          size = 0;
          current = null;
     public void add (T element)
          boolean notBegin = true;
          size = size + 1;
          if (isEmpty())
               current = new DoubleNode<T>(element);
          while (current.getPrevious() != null)
               current = current.getPrevious();
          Comparable<T> cElement = (Comparable<T>)element;
          while (cElement.compareTo(current.getElement()) > 0)
               if (current.getNext() != null)
                    current = current.getNext();
               else
                    notBegin = false;
          if (notBegin)
               DoubleNode<T> temp = new DoubleNode<T>(element);
               DoubleNode<T> temp2 = current;
               current.setPrevious(temp);
               temp.setNext(current);
               temp.setPrevious(temp2.getPrevious());
               current = temp;
          else
               DoubleNode<T> temp = new DoubleNode<T>(element);
               while (current.getPrevious() != null)
                    current = current.getPrevious();
               temp.setNext(current);
               current.setPrevious(temp);
     public T removeFirst()
          try
               if (isEmpty())
                    throw new EmptyCollectionException("List");
          catch (EmptyCollectionException e)
               System.out.println(e.getMessage());
          while (current.getPrevious() != null)
               current = current.getPrevious();
          DoubleNode<T> temp = current;
          current = temp.getNext();
          size = size - 1;
          return temp.getElement();
     public T removeLast()
          try
               if (isEmpty())
                    throw new EmptyCollectionException("List");
          catch (EmptyCollectionException e)
               System.out.println(e.getMessage());
          while (current.getNext() != null)
               current = current.getNext();
          DoubleNode<T> temp = current;
          current = temp.getPrevious();
          size = size - 1;
          return temp.getElement();
     public T first()
          try
               if (isEmpty())
                    throw new EmptyCollectionException("List");
          catch (EmptyCollectionException e)
               System.out.println(e.getMessage());
          while (current.getPrevious() != null)
               current = current.getPrevious();
          return current.getElement();
     public T last()
          try
               if (isEmpty())
                    throw new EmptyCollectionException("List");
          catch (EmptyCollectionException e)
               System.out.println(e.getMessage());
          while (current.getNext() != null)
               current = current.getNext();
          return current.getElement();
     public int size()
          return size;
     public boolean isEmpty()
          if (size == 0)
               return true;
          else
               return false;
     public String toString()
           return "An ordered linked list.";
}the other file that uses this class:
import java.io.*;
import java.util.StringTokenizer;
public class ListBuilder
     public static void main(String[] args) throws IOException
          String input;
          StringTokenizer st;
          int current;
          OrderedLinkedList<Integer> list = new OrderedLinkedList<Integer>();
          FileReader fr = new FileReader("C://TestData.txt");
          BufferedReader br = new BufferedReader(fr);
          input = br.readLine();
          while (input != null)
               st = new StringTokenizer(input);
               while (st.hasMoreTokens())
                    current = Integer.parseInt(st.nextToken());
                    if (current != -987654321)
                         list.add(current);
                    else
                         try
                              unload(list);
                         catch(EmptyCollectionException f)
                              System.out.println(f.getMessage());
               input = br.readLine();
          System.out.println("Glad That's Over!");
     public static void unload(OrderedLinkedList<Integer> a) throws EmptyCollectionException
          while (!a.isEmpty())
               System.out.println(a.removeFirst());
               if (!a.isEmpty())
                    System.out.println(a.removeLast());
          System.out.println("That's all Folks!\n");
}

Answer 1

i tried @SuppressWarnings("unchecked") and that didnt work. so i ran it and it showed these errors:
Exception in thread "main" java.lang.NullPointerException
at OrderedLinkedList.add(OrderedLinkedList.java:30)
at ListBuilder.main(ListBuilder.java:32)
Press any key to continue...
which would be:
          while (current.getPrevious() != null)and:
                         list.add(current);