Question

Static methods can be called directly from the name of the class that contains the method. Static methods are usually created to do utility operations. For example:

public class Test{
public static int timesTwo(int value){
return value * value;
}
}

public class TestDriver{
public static void main(String[] args){
int var = Test.timesTwo(5);
  System.out.println(var);
}
}

For your final exercise, create a class called ManyLinkedLists. It will contain a static method called createLinkedList(). That method takes an argument that is a constant defined in the ManyLinkedLists class. The identifier of the constants should describe a type of linked list. When the createLinkedList method is called, it should return a linked list object of the type identified by the constant.

For example:

DoubleEndedList del = ManyLinkedLists.createLinkedList(ManyLinkedLists.DOUBLEENDEDLIST);

Give the createLinkedList method the ability to return the linked lists described below:

• A double-ended linked list.
• A doubly linked list.

Use a long instance variable as the data within your link class or classes.
Your project should contain any other classes you need. Include a ManyLinkedListsDriver class that tests the ManyLinkedLists class, its method, and the data structures that the method can return. The peculiar features of the two forms of linked list should be clearly demonstrated.

Include a document in your submitted project that clearly explains the difference between a double-ended linked list and a doubly linked list.

Answer 1

The Linked List that is mentioned in the question must possess two features.

1. Doubly Linked list: The Doubly Linked list the one in which the node has pointers to both next pointer and the previous pointer. Whereas in case of a singly linked list, the node has only the next pointer.

2. Double Ended Linked List: The double ended linked list is similar to that of a deque. The elements can be inserted from either side of a list.

Implementation: The node is has a data associated with the pointers. Hence we have to make a class called Node. We must also specify the methods that are required for inserting or deleting the elements to the list.

class Node{

public: int data;

             Node next;

             Node prev;

public:

    Node(int data){

        this.data = data;

        this.next = null;

        this.prev = null;

    }

}

class Deque{

    public: Node head, tail;

    public void addFirst(int data){

        Node node = new Node(data);

        if(head == null){

            head = node;

            tail = node;

        }else{

            node.next = head;

            head.prev = node;

            head = node;

        }

    }

    public void addLast(int data){

        Node node = new Node(data);

        if(head == null){

            head = node;

            tail = node;

        }else{

            tail.next = node;

            node.prev = tail;

            tail = node;

        }

    }

    public void pollFirst(){

        if(head == null) System.out.println("List is empty");

        if(head == tail){

            head = tail = null;

        }

        else{

            Node temp = head;

            head = head.next;

            temp.next = null;

            head.prev = null;

        }

    }

    public void pollLast(){

        if(head == null) System.out.println("List is empty");

        if(head == tail){

            head = tail = null;

        }

        else{

            Node temp = tail;

            tail = tail.prev;

            temp.prev = null;

            tail.next = null;

        }

    }

}

class ManyLinkedLists{

    Node createLinkedList(){

        Deque d = new Deque();

        return d.head; // returning the head of the list

    }

}