Alphabetically ordering a Linked List

Question

Would anyone please be able to give me help in ordering a linked list alphabetically. I'm new to java so please be gentle.
Many thanks in advance.

Answer 1

I've just tried that but it gave me errors on trying to compile it:
.\List.java:91: Incompatible type for method. Explicit cast needed to convert List to java.util.List.
     Collections.sort(leftList);
     ^
.\List.java:92: Incompatible type for method. Explicit cast needed to convert List to java.util.List.
     Collections.sort(rightList);
     ^
2 errors
I'll post my coding below to see if you can help me out. Thanks a lot.
import java.util.LinkedList;
import java.util.Collections;
class ListNode {
// package access data so class List can access it directly
char data;
ListNode next;
// Constructor: Create a ListNode that refers to Object o.
ListNode( char c ) { this( c, null ); }
// Constructor: Create a ListNode that refers to Object o and
// to the next ListNode in the List.
ListNode( char c, ListNode nextNode )
data = c; // this node refers to Object o
next = nextNode; // set next to refer to next
// Return a reference to the Object in this node
char getChar() { return data; }
// Return the next node
ListNode getNext() { return next; }
// Class List definition
public class List {
private ListNode firstNode, current;
private ListNode lastNode;
private String name; // String like "list" used in printing
// Constructor: Construct an empty List with s as the name
public List( String s )
name = s;
firstNode = lastNode = null;
// Constructor: Construct an empty List with
// "list" as the name
public List() { this( "list" ); }
public synchronized boolean isEmpty()
{ return firstNode == null; }
public synchronized void insertAtBack( char insertItem )
if ( isEmpty() )
firstNode = lastNode = new ListNode( insertItem );
else
lastNode = lastNode.next = new ListNode( insertItem );
print();
// System.out.println(insertItem);
     // public char getText(){
     // return current.data;
// Output the List contents
public synchronized void print()
     current = firstNode;
while ( current != null ) {
System.out.print(current.data);
current = current.next;
System.out.println( "\n" );
// method to split the linked list
public synchronized void splitList(){
          System.out.println("splitList");
          ListNode present = firstNode;
List leftList = new List();     // create the left list
List rightList = new List();     // create the right list
          try{
               while (present != null) {
                    leftList.insertAtBack(present.data);
                    System.out.println("left " +present.data);
                    present = present.next; // skips 1 node
                    rightList.insertAtBack(present.data);
                    System.out.println("right " +present.data);
                    present = present.next; // skips 1 node
     Collections.sort(leftList);
     Collections.sort(rightList);
          catch(NullPointerException e){