Circular Queue ADT using Linked Lists.

Hi guys here is a code on Circular Linked List in Java! Program :

import java.util.Scanner;
interface CllAdt{
    public void insert();
    public void delete();
    public void display();
    public int len();
}
class CNode{
    int data;
    CNode link;
}
public class CQSll extends CNode implements CllAdt{
    CNode first;
    Scanner s=new Scanner(System.in);
    public CQSll(){
        first=null;
    }

    public void insert(){
        System.out.println("Enter the position to insert a node :");
        int pos=s.nextInt();
        System.out.println("Enter the data into a node :");
        int ele=s.nextInt();
        
        CNode p=new CNode();
        p.data=ele;
        p.link=null;
        CNode temp;
        if(pos<1 || pos>len()+1)
            System.out.println("Invalid position and insertion is  not possible");
        else if(pos==1&&len()==0)
        {
            first=p;
            first.link=first;
            System.out.println("Entered position is(1st):"+pos);
        }
        else if((pos==1)&&(len()!=0)){
            temp=first.link;
            while(temp.link!=first)
                temp=temp.link;
            p.link=first;
            first=p;
            temp.link=first;
            System.out.println("Entered position is(1st):"+pos);
        }
        else if(pos==len()+1){
            temp=first;
            while(temp.link!=first)
                temp=temp.link;
            temp.link=p;
            p.link=first;
            System.out.println("Entered position is(Last) :"+pos);
        }
        else
        {
            temp=first;
            for(int i=1;i<pos-1;i++)
                temp=temp.link;
            
            p.link=temp.link;
            temp.link=p;
            System.out.println("Entered position is:"+pos);
        }
    }

    public void delete(){
        System.out.println("Enter the position to delete a node :");
        int pos=s.nextInt();
        CNode p,temp;
        if(pos<1||(pos>len()+1)||(len()==0))
            System.out.println("Invalid position and deletion is not possible");
        else if(pos==1&& len()==1){
            temp=first;
            first=null;
            System.out.println("Only one i.e. Deleted item:"+temp.data);
        }
        else if(pos==1&&len()!=1){
            temp=first.link;
            while(temp.link!=first)
                temp=temp.link;
            p=first;
            first=p.link;
            temp.link=first;
            System.out.println("From begininning i.e. Deleted item :"+p.data);
        }
        else if(pos==len()){
            temp=first;
            for(int i=1;i<pos-1;i++)
                temp=temp.link;
            p=temp.link;
            temp.link=first;
            System.out.println("From Ending i.e. Deleted item :"+p.data);
        }
        else{
            temp=first;
            for(int i=1;i<pos-1;i++)
                temp=temp.link;
            p=temp.link;
            temp.link=p.link;
            System.out.println("Deleted item :"+p.data);
        }
    }

    public void display(){
        CNode temp;
        if(first==null)
            System.out.println("Circular Linked list is empty :");
        else{
            System.out.println("List of elements :");
            System.out.println("First->");
            temp=first;
            System.out.println(temp.data+"-->");
            temp=first.link;
            while(temp!=first){
                System.out.println(temp.data+"-->");
                temp=temp.link;
            }
            System.out.println("End");
        }
    }
    @Override
    public int len(){
        int count=1;
        CNode temp=first;
        if(temp==null) return(0);
        else if(temp.link==first) return(1);
        else{
            while(temp.link!=first){
                count++;
                temp=temp.link;
            }
            return count;
        }
    }
    public static void main(String args[]){
        System.out.println("Circular Linked List ADT");
        Scanner s=new Scanner(System.in);
        CQSll c=new CQSll();
        String ch="y";
        while(ch.equalsIgnoreCase("y")){
            System.out.println("\n CLL Operations :");
            System.out.println("1. Insert 2. Delete 3. Display 4. Length 5. Exit :");
            System.out.println("Enter the option :");
            int opt=s.nextInt();
            switch(opt){
                case 1: c.insert();break;
                case 2: c.delete();break;
                case 3: c.display();break;
                case 4: System.out.println("Length of CLL is :"+c.len());
                case 5: System.exit(0);
                case 6: System.out.println("Invalid option!");
            }
            System.out.println("\nDo you want to continue(y/n)");
            ch=s.next();
        }
    }
}