I've a problem to my linkedlist at line 10. Can anyone help me to solve it? Thank in advance.

edcc2efd2d7051037a9a147491e15671

This is my code :

package linkedlist;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class LinkedList 
{   
    private String firstName;
    private String lastName;
    private static LinkedList<LinkedList> classRoster  = new LinkedList<LinkedList>();
    class C {
    int i;
    String s;

    C(){
        System.out.println("In main constructor");
        // Other processing
    }

    C(int i){
        this(i,"Blank");
        System.out.println("In parameterized constructor 1");
    }

    C(int i, String s){
        System.out.println("In parameterized constructor 2");
        this.i = i;
        this.s = s;
        // Other processing
        // Should this be a copy-paste from the main contructor?
        // or is there any way to call it?
    }
    public void show(){
        System.out.println("Show Method : " + i + ", "+ s);
    }
}

    private static class Node
    {
        LinkedList data;
        private Node next = null;

        private Node(LinkedList data, Node next)
        {
            this.data = data;
            this.next = next;
        }

        private Node(LinkedList data)
        {
            this.data = data;
        }

        public LinkedList getData()
        {
            return data;

        }

    }

    private static Node head;

    /**
     * Default Constructor
     */
    public LinkedList()
    {
        head = null;
    }

    /**
     * Constructor
     * @param firstName First name of student
     * @param lastName  Last Name of Student
     */
    public LinkedList(String firstName, String lastName)
    {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    public void addToStart(LinkedList data)
    {
        head = new Node(data, head);
    }
    /**
     * Getter for firstName
     * @return firstName
     */
    public String getFirstName() 
    {
        return firstName;
    }

    /**
     * Setter for firstName
     * @param firstName
     */
    public void setFirstName(String firstName) 
    {
        this.firstName = firstName;
    }
    /**
     * Getter for lastName
     * @return lastName
     */
    public String getLastName() 
    {
        return lastName;
    }

    /**
     * Setter for Last Name
     * @param lastName
     */
    public void setLastName(String lastName) 
    {
        this.lastName = lastName;
    }

    /**
     * toString method used for testing
     */


    public String toString() 
    {
        return "linkedList [firstName=" + firstName + ", lastName="
                + lastName + "]";
    }

    /**
     * Prints out list to console
     */
    public void printList() 
    {
        int count = 0;
        System.out.println("First Name:     " + "Last Name: ");
        while (count < classRoster.size())
        {
            LinkedList a = classRoster.get(count);
            System.out.println(a.getFirstName() + "     \t" + a.getLastName());
            count++;
        }

    }
    /**
     * 
     * @param a linked list ran in 
     */
    public static void addToList(LinkedList a)
    {
        Node temp = head;
        Node nextNode = null;
        while (temp != null && nextNode.data.compareTo(a) >=0)
        {
            nextNode = temp;
            temp = temp.next;
        }
        if (temp == null)
        {
            Node cur2 = new Node(a);
            cur2.next = head;
            head = cur2;    
            classRoster.add(cur2.getData());
        }
        else {

            Node cur2 = new Node(a);
            cur2.next = temp;
            if (nextNode == null) {
                nextNode.next = cur2;
                classRoster.add(cur2.getData());
            }
        }
    }

    /**
     * Reads in students names into object then adds and sorts list based on last name & firstName
     * @param inputFileName The File Name
     * @throws java.io.IOException
     */
    public void read(String inputFileName) throws java.io.IOException
    {
    Scanner infile = new Scanner(new FileReader(inputFileName));
    while(infile.hasNext())
    {
    String firstName = infile.next();
    String lastName = infile.next();

    LinkedList intoList = new LinkedList(firstName, lastName);
    LinkedList.addToList(intoList);

    }
    infile.close();
    }

    public static void main(String[] args) throws IOException 
    {
        LinkedList test = new LinkedList();
        test.read("179ClassList.txt");
        test.printList();
    }

    public int compareTo(LinkedList arg0)
    {
        if (this.lastName.equals(arg0.getLastName()))
            return this.firstName.compareTo(arg0.getFirstName());
        else
            return this.lastName.compareTo(arg0.getLastName());
    }
}
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