Question & Answer: Below is some code of a linked list in java, my addLast method will not work and I have no idea why! when i state…..

The way that head and tail nodes were initialized as separate Nodes rather than only one node with Head and tail pointing to the same Node, led to head and tail being disjoint nodes as a result any future additions either in front or back didn’t reflected in the list.

This is the complete working code of the LinkList program

public class LinkedList {

Node head;
Node tail;

int size;

public LinkedList(){

head =null;
tail = null;
size = 0;
}

private void addfirst(String data){

if (size == 0){
Node temp=new Node(data);
head=temp;
tail=temp;
size++;

}else{

Node newn = new Node(data);
newn.setNext(head);
head = newn;

size++;
}
}

private void addLast(String data){

if(size == 0){
Node temp=new Node(data);
head=temp;
tail=temp;
size++;

}else{

Node newn = new Node(data);

tail.setNext(newn);

tail = newn;

size++;
}

//       Node current = head;
//       while(current != null){
//           if(current.getNext() == null){
//               Node newnn = new Node(“test”);
//            current.setNext(newnn);
//            size++;
//            return;
//           }
//           current = current.getNext();
//       }
//

}

private Node removeLast(){
Node current = head;

while(current.getNext() != null){

if(current.getNext() == tail){

Node temp = tail;
current.setNext(null);
tail = current;
return temp;

}else{
current = current.getNext();
}

}
return null;
}
private Node removei(String data){

if(head.getData() == data){

Node temp = head;
head = head.getNext();
return temp;

}

Node current = head;

while(current.getNext() != null){

if(current.getNext().getData() == data){
Node temp = current.getNext();
current.setNext(current.getNext().getNext());
return temp;

}
current = current.getNext();
}
return null;
}

private void reverse(){

Node current = head;
Node previous = null;
Node next = null;

while(current != null){
next = current.getNext();
current.setNext(previous);
previous = current;
current = next;

}
head = previous;

}

private void print(){

Node current = head;

while (current!= null){

System.out.println(current.getData());

current = current.getNext();
}

}
public static void main(String[] args) {
LinkedList l = new LinkedList();

l.addfirst(“4”);
l.addfirst(“3”);
l.addfirst(“2”);
l.addfirst(“1”);

l.print();
System.out.println(“—————–“);
//l.removeLast();
//l.addNodetoend(“end”);
// System.out.println(“Last:”+l.tail.getData());
l.addLast(“end”);
l.addLast(“end1”);
l.addLast(“end2”);
l.addLast(“end3”);
l.addLast(“end4”);
l.print();
//System.out.println(“Last:”+l.size);

}

}