Question

please modify the method public void addList(SinglyLinkedList<E> s) that add list to another with addlast() and remove() methods without changing the parameter of addList method.

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public class SinglyLinkedList<E> {

     private class Node<E> {

           private E element;

           private Node<E> next;

           public Node(E e, Node<E> n) {

                element = e;

                next = n;

           }

           public E getElement() {

                return element;

           }

           public void setElement(E element) {

                this.element = element;

           }

           public Node<E> getNext() {

                return next;

           }

           public void setNext(Node<E> next) {

                this.next = next;

           }

     }

     private Node<E> head = null;

     private Node<E> tail = null;

     private int size = 0;

     public SinglyLinkedList() {

     }

     public void size() {

           System.out.println(size);

     }

     public boolean isEmpty() {

           return size == 0;

     }

     public E first() {

           if (isEmpty())

                return null;

           return head.getElement();

     }

     public E last() {

           if (isEmpty())

                return null;

           return tail.getElement();

     }

     public void add(E e) {

           head = new Node<>(e, head);

           if (size == 0)

                tail = head;

           size++;

     }

     public void addLast(E e) {

           Node<E> newest= new Node<>(e, null);

           if (isEmpty()) head=newest;

           else tail.setNext(newest);

           tail=newest;

           size++;

     }

     public void addFirst(E e) {

           head= new Node<>(e, head);

           if (size==0) tail=head;

           size++;

     }

     public void display() {

           Node<E> current = head;

           if (head == null) {

                System.out.println("List is empty");

                return;

           }

           System.out.println("Nodes of singly linked list: ");

           while (current != null) {

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

                current = current.next;

           }

           System.out.println();

     }

     public void addList(SinglyLinkedList<E> s) {

           Node<E> current= s.head;

           while (current!=null) {

                addLast(current.element);

                current.getNext();

           }

           tail=s.tail;

           size+=s.size;

     }

}

Answer 1

Updation done in the code :

in the method public void addList(SinglyLinkedList<E> s){}

with the current code it was going into infinite loop

Reason for infinite loop : the variable current was not getting updated , ie for every iteration , current must be updated with current.getNext(). With the current code current.getNext() was called but its value was never getting updated in current variable. So a minor change in the code fixed it.

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Please find the main method to test the code and output below:

Please find the actual code for SinglyLinkedList class below:

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class SinglyLinkedList<E> {
private class Node<E> {
private E element;
private Node<E> next;
public Node(E e, Node<E> n) {
element = e;
next = n;
}
public E getElement() {
return element;
}
public void setElement(E element) {
this.element = element;
}
public Node<E> getNext() {
return next;
}
public void setNext(Node<E> next) {
this.next = next;
}
}

private Node<E> head = null;

private Node<E> tail = null;

private int size = 0;

public SinglyLinkedList() {
}

public void size() {
System.out.println(size);
}

public boolean isEmpty() {
return size == 0;
}

public E first() {
if (isEmpty())
return null;
return head.getElement();
}

public E last() {
if (isEmpty())
return null;
return tail.getElement();
}

public void add(E e) {
head = new Node<>(e, head);
if (size == 0)
tail = head;
size++;
}

public void addLast(E e) {
Node<E> newest = new Node<>(e, null);
if (isEmpty())
head = newest;
else
tail.setNext(newest);
tail = newest;
size++;
}

public void addFirst(E e) {
head = new Node<>(e, head);
if (size == 0)
tail = head;
size++;
}

public void display() {
Node<E> current = head;
if (head == null) {
System.out.println("List is empty");
return;
}
System.out.println("Nodes of singly linked list: ");
while (current != null) {
System.out.println(current.getElement());
current = current.next;
}
System.out.println();
}

public void addList(SinglyLinkedList<E> s) {
Node<E> current = s.head;
while (current != null) {
addLast(current.element);
current = current.getNext(); //this line was updated
}
tail = s.tail;
size += s.size;
}

}