Need help with linked list

public class KLink{
 	
   public Node head;
 	
   // inner class Node 
   public class Node{
 		char data;
 		Node next;
 		Node(char a){data = a; next = null;}
 	}
 
 	public KLink(){head = null;}
 
   public void delete(char a){
 			
 	 // empty list
 	   if(head == null){System.out.println("Delete on empty list");}
 			
 		 // first element delete
 		 if(a == head.data){
 			   head = head.next;
 				 return;
 			}
 			
 			Node curr = head;
 			Node prev = null;
 			while(curr != null){
 			   if(a == curr.data)break;
 			   prev = curr;
 				 curr = curr.next;
 			}
 			
 		  // remove in middle
 			if(curr != null){
 			   prev.next = curr.next;
 			   return;
 			}
 			
 			// remove from end
 			prev = null;
 	}
 	
 	public void add(char a){
 		Node addon = new Node(a);
 		
 		// add to empty list
 		if(head == null){
 		   head = addon;
 			 return;
 		}
 		
 		// add to beginning of list
 		if(a < head.data){
 		   addon.next = head;
 			 head = addon;
 		   return;
 		}
 		
 		// add to middle/end
 		
 		// find insertion point
 		Node prev = null;
 		Node curr = head;
 		while(curr != null){
 		   if(a < curr.data){
 				   break;
 			 }
 			 prev = curr;
 			 curr = curr.next;
 		}
 		
 		// insert in middle
 		if(curr != null){
 		   prev.next = addon;
 			 addon.next = curr;
 			 return;
 		}
 		
 		// add to end
 		prev.next = addon;
 		
 	}
 	
 	public void print(String msg){	
 		Node curr = head;
 		System.out.println(msg);
 		if(curr == null){
 			System.out.println("Empty List");
 			return;
 		}
 		while(curr != null){
 			System.out.println(curr.data );
 			curr = curr.next;
 		}
 	}
 	
 	public boolean empty(){
 	   return head == null;
 	}
 }
 

 public Node head; 
public Node tail; 
  
   // inner class Node 
public class Node
{
	char data;
			 Node next;
			 Node previous;
   
			 Node(char a)
			 {data = a; next = null;}
}

 

public void add(char a)

{ 
Node addon = new Node(a); 

// add to empty list 

if (head == null)

{ 

head = tail = addon; 

return; 

} 

// add to beginning of list 

if(a < head.data)

{ 
addon.next = head;
addon.previous = null; 
head = addon; 
return; } 

// add to middle/end 

// find insertion point 

Node prev = null; 

Node curr = head; 

while(curr != null)

{ 

if(a < curr.data)

{ 
break; 
} 

prev = curr; 
curr = curr.next; 

} 

// insert in middle 

if(curr != null)

{ 
prev.next = addon;
addon.previous = prev; 
addon.next = curr;
curr.previous = addon; 
return; 
}

// add to end 

prev.next = addon; 
addon.previous = prev; 

}