Recursion on a LinkedList

[chetah]

public class LinkedList<T>{
    private Node head;
    
    
    public LinkedList()
    {
        head = null;
    }
    
    public boolean isEmpty()
    {
        return (head==null);
    }
    
    public void addToHead(T val )
    {
        Node n = new Node(val);
        n.next = head;
        head   = n;
    }
    
    
    public T getHeadData(){
        if(head == null){
            throw new RuntimeException("attempt to get data from an empty list !");
        }
        else{
            return head.data;
        }
    }
    
    public void deleteHead(){
        if(head ==  null){
            throw new RuntimeException("Deleting from an empty list !");
        }else{
            head= head.next;
        }
    }

    public void addToTail(T val)//show no result
    {
        Node n = new Node (val);    
        if(head==null)
            head = n;
        else{
            Node curr = head;
            curr = curr.next;
            curr.next = n;
            addToTail(val);
        }    
    }//end addtail


    
    public void delete(T val){//does not return a result (shows no errors)
        Node curr=null;
        if(head !=null){
            if(head.data==val)
                head = head.next;
            else{
                curr = head;
                curr = curr.next;
                delete(curr.data);
            }
        }
    }
    
    public void insertSorted(T val){
        Node y = new Node(val);
        
        if(head==null || val < head.data)//operator < cannot be applied to T, T
            head = y;
        else
            head = head.next;
            insertSorted(head.data);
    }
    
    
    public boolean contains(T val)
    {
            
        if(head!=null){
            if(head.data==val)
                return true;
                head = head.next;
            return contains(val);
        }
        return false;
    
    }//end of contains
    
        
    public String toString(){
        String str = " ";
        Node curr = head;
        while(curr !=null){
            str = str + curr.data +" ";
            curr = curr.next;
        }
        return str + "\n";
    }
    
    
    public class Node{
        public T data;
        public Node next;
        
        public Node(T val){
            data = val;
            next = null;
        }
    }//End of node class
}//Linked List


class TestLinkedList{
    public static void main(String[] args){
        
        LinkedList<Integer>ST = new LinkedList<Integer>();
        
        for(int i = 0; i < 10; i++){  //correctly load linkedlist
            ST.addToHead(i);
        }
        
        
            System.out.println(ST.toString()); //print list
            
                    
            boolean y = ST.contains(12);
           System.out.println(y);

       
           ST.addToTail(200); //returns nothing
               System.out.println(ST.toString());
           
                      
            ST.delete(5);
            System.out.println(ST.toString());

            insertSorted(11);
            System.out.println(ST.toString());
        
    }//end main
}//end class

Need help.
public void addToTail(T val)
public void delete(T val)
public void insertSorted(T val)
I need help to get the above functions to work recursively.  I am able to get them work iteratively, no problem.  When I try to write the functions re cursively, I am not able to see any results. I am at a lost understanding why.

[jkmyoung]

public void addToTail(T val)
public void delete(T val)
public void insertSorted(T val)

You need to create functions pointing to the Nodes.
Each Node does not point to a LinkedList, it points to another Node!

eg create a function
private void addToTail(T val, Node n)

public void addToTail(T val){
  base case // need to check if there exists a node..otherwise
  addtoTail(val, head);
}
private void addToTail(T val, Node n){
  if (n.next = null){
    n.next = new Node(val);
  } else {
    addToTail(val, n.next)
  }
}

Do something similar for the rest and you should be set.

[chetah]

Call from main

Thanks you very much for your response. However, I still have a problem, when I am call a function from the main program.

public static void main(etc){

ST.addToTail(No de x, 12) // I am unable to access the Node class from LinkedList.
where am I going wrong?

[jkmyoung]

Are you calling it from the main program? It should just be:
ST.addToTail(12 )

The class will then call addToTail(head, 12) on itself