Write a JAVA LinkedListRec class that has the following meth

Write a JAVA LinkedListRec class that has the following methods: size, empty, insertBefore, insertAfter, addAtHead, addAtEnd, remove, replace, peekFront, peekEnd, removeFront, removeEnd, toString. Use recursion to implement most of these methods. Write a driver to test your implemented LinkedListRec class methods.

Solution

import java.util.Scanner;
public class LinkedListRec {
    int data;
    LinkedListRec prev=null,next=null;
  
    int size(LinkedListRec l)//method which returns the length of the list
    {
        if(l==null)return 0;
        return 1+size(l.next);
    }
    boolean empty(LinkedListRec l)//method checks whether the list is empty or not...
    {
        if(l==null)return true;
        else return false;
    }
    LinkedListRec insertBefore(LinkedListRec l,int value,int num_insertbefore)//method which adds a new number before the given number..
    {
        if(l==null)return l;
        if(l.data == num_insertbefore)
        {
            LinkedListRec n = new LinkedListRec();
            n.data = value;
            if(l.prev==null)
            {
                n.next = l;
                l=n;
            }
            else
            {
                n.prev = l.prev;
                n.next= l;
                l.prev = n;
            }
            return l;
       }
        return insertBefore(l.next,value,num_insertbefore);
  
    }
  
    LinkedListRec insertAfter(LinkedListRec l,int value,int num_insertafter)//method which adds the new number after the given number
    {
        if(l==null)return l;
        if(l.data == num_insertafter)
        {
            LinkedListRec n = new LinkedListRec();
            n.data = value;
            if(l.next==null)
            {
                l.next = n;
                n.prev = l;
            }
            else
            {
                n.next = l.next;
                l.next.prev = n;
                n.prev = l;
            }
            return l;
       }
        return insertAfter(l.next,value,num_insertafter);
  
    }
    LinkedListRec addAtHead(LinkedListRec l,int value)//method which adds a new number at the head position of the list...
    {
        LinkedListRec n = new LinkedListRec();
    n.data=value;
    n.next = l;
    l=n;
    return l;
    }
    LinkedListRec addAtEnd(LinkedListRec l,int value)//method which adds a new number at the end position of the list...
    {
        if(l==null){ l = new LinkedListRec();l.data = value;return l;}
        if(l.next==null)
        {
        LinkedListRec n = new LinkedListRec();
        n.data=value;
        n.prev = l;
        l.next = n;
        return l;
        }
        return addAtEnd(l.next,value);
    }
    LinkedListRec remove(LinkedListRec l,int value)//method which removes given numbet from the list....
    {
        if(l==null)return l;
        if(l.data == value)
        {
            if(l.prev!=null){
            l.prev = l.next;
            }
            else
                l=l.next;
            return l;
        }
        return remove(l.next,value);
    }
    boolean replace(LinkedListRec l,int value,int newvalue)//method which replaces current number with new number,...
    {
        if(l==null)return false;
        if(l.data == value)
        {
            l.data = newvalue;
            return true;
        }
        return replace(l.next,value,newvalue);
    }
    int peekFront(LinkedListRec l)//method which returns the first value of the list...
    {
    if(l!=null)  
    return l.data;
    else return -1;
    }
    int peekEnd(LinkedListRec l)//method which returns the last value of the list........
    {
        if(l==null)return -1;
        if(l.next == null)return l.data;
        return peekEnd(l.next);
  
    }
    LinkedListRec removeFront(LinkedListRec l)//method which removes the first element of the list..
    {
        if(l==null)return l;
        l=l.next;
        return l;
    }
    boolean removeEnd(LinkedListRec l)//method which removes the last element of the list//
    {
      
        if(l.next==null)
        {
            if(l.prev!=null){l.prev.next=null;return true;}
            l.data = -1;
            return true;
        }
        return removeEnd(l.next);
    }
    String tostring(LinkedListRec l)//displaying list
    {
        if(l==null)return \"\";
        System.out.print(l.data+\"->\");
        return l.data+\"->\"+tostring(l.next);
  
    }

    public static void main(String argv[])
    {
        //driver testing code...
        LinkedListRec ll = new LinkedListRec();
        ll.data = 2;
        Scanner sc = new Scanner(System.in);
        int c=-2;
        while(true)
        {
            System.out.println(\"Select on option(-1 to exit)\ 1: size of list\ 2: is list empty\ 3: insert Before a number\ 4:insert After a number\ 5: add At head\ 6: add at End\ 7: remove from list\ 8: Replace a value\ 9: peekfrontvalue\ 10:peekendvalue\ 11:removefrontvalue\ 12:removeendvalue\ 13:display\");
            System.out.print(\"Enter ur choice\");
            c = sc.nextInt();
            if(c==-1)break;
            if(c==1){
                System.out.println(\"\ Size of List:\"+ll.size(ll));
              
            }
            else if(c==2){
                if(ll.empty(ll))
                    System.out.println(\"\ List is Empty\ \");
                else System.out.println(\"\ List is not Empty\ \");
            }
            else if(c==3){
                int v,p;
                System.out.println(\"\ Enter number to insert:\");
                v = sc.nextInt();
                System.out.println(\"\ Enter number to insertBefore it:\");
                p = sc.nextInt();
                ll=ll.insertBefore(ll, v, p);
            }
            else if(c==4){
          
                int v,p;
                System.out.println(\"\ Enter number to insert:\");
                v = sc.nextInt();
                System.out.println(\"\ Enter number to insertAfter it:\");
                p = sc.nextInt();
                ll.insertAfter(ll, v, p);
            }
            else if(c==5){
                int v;
                System.out.println(\"\ Enter number to insert:\");
                v = sc.nextInt();
               ll= ll.addAtHead(ll, v);
            }
            else if(c==6){
                int v;
                System.out.println(\"\ Enter number to insert:\");
                v = sc.nextInt();
                ll=ll.addAtEnd(ll, v);
            }
            else if(c==7){
                int v;
                System.out.println(\"\ Enter number to remove:\");
                v = sc.nextInt();
                ll=ll.remove(ll, v);
             }
            else if(c==8){
                int v,p;
                System.out.println(\"\ Enter number to replace:\");
                v = sc.nextInt();
                System.out.println(\"\ Enter which number to replace:\");
                p = sc.nextInt();
                ll.replace(ll, v, p);
            }
            else if(c==9){
          
                System.out.println(\"\ Front value of the list:\"+ll.peekFront(ll));
            }
            else if(c==10){
                System.out.println(\"\ End value of the list:\"+ll.peekEnd(ll));
            }
            else if(c==11){
                ll=ll.removeFront(ll);
              
                    System.out.println(\"\ Front value of the list is removed\");
             
            }
            else if(c==12){
                if(ll.removeEnd(ll))
                {
                    System.out.println(\"\ Front value of the list is removed\");
                }
            }
            else if(c==13){
                System.out.println(\"\ The list:\");
                ll.tostring(ll);
                System.out.println();
            }
     
        }
      
    }

}

ouput:

run:
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice8

Enter number to replace:
2

Enter which number to replace:
7
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice13

The list:
7->
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice9

Front value of the list:7
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice6

Enter number to insert:
9
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice13

The list:
7->9->
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice1

Size of List:2
Select on option(-1 to exit)
1: size of list
2: is list empty
3: insert Before a number
4:insert After a number
5: add At head
6: add at End
7: remove from list
8: Replace a value
9: peekfrontvalue
10:peekendvalue
11:removefrontvalue
12:removeendvalue
13:display
Enter ur choice-1