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 o.

1. 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;

2. }
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);

3. }
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;

4. }
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//
{

5. 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));
}

6. 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;

7. 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();
}

8. }
}
}
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. 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

10. 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

11. 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