Question

You must write an appropriate code for all member methods so that a double-linked list functionality can be obtained. Changes to the class definition, instance variables, and signatures of the membership method are not allowed. This class has no main method.

package javaclass;

/**

* The class for doubly-linked data structures. Provides attributes

* and implementations for getLength, isEmpty, and toArray methods.

* The head attribute is the first node in any doubly-linked list and

* last is the last node.

*

* @author

* @version 2017-11-01

*

*/

public class DoubleLink {

// First node of double linked list

private DoubleNode head = null;

// Number of elements currently stored in linked list

private int length = 0;

// Last node of double linked list.

private DoubleNode last = null;

/**

   * Adds a new Movie element to the list at the head position

   * before the previous head, if any. Increments the length of the List.

*

   * @param value

   * The value to be added at the head of the list.

*

   * @return true if node is added successfully, else false.

   */

public final boolean addNode(final Movie value) {

//your code here

return false;//you must change this statement as per your requirement

}

/**

   * Removes the value at the front of this List.

   *

   * @return The value at the front of this List.

   */

public Movie removeFront() {

// your code here

return null;//you must change this statement as per your requirement

}

/**

   * Returns the head element in the linked structure. Must be copy safe.

   *

   * @return the head node.

   */

public final DoubleNode getHead() {

//your code here

return null;//you must change this statement as per your requirement

}

/**

   * Returns the current number of elements in the linked structure.

   *

   * @return the value of length.

   */

public final int getLength() {

//your code here

return -1;//you must change this statement as per your requirement

}

/**

   * Returns the last node in the linked structure. Must be copy safe.

   *

   * @return the last node.

   */

public final DoubleNode getLast() {

//your code here

return null;//you must change this statement as per your requirement

}

/**

   * Determines whether the double linked list is empty or not.

   *

   * @return true if list is empty, false otherwise.

   */

public final boolean isEmpty() {

//your code here

return true;//you must change this statement as per your requirement

}

/**

   * Returns all the data in the list in the form of an array.

   *

   * @return The array of Movie elements. Must be copy safe

   */

public final Movie [] toArray() {

//your code here

return null;//you must change this statement as per your requirement

}

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

DoubleNode class

package doubleNode;

/**
*The individual node for a double-linked structure where movies are stored * objects. This is a double-linked node. The node link can be updated, * but not node data to prevent data moving between nodes. * Data structures must be rearranged by moving nodes.
*
* @author
* @version 2010-10-09
*/
public final class DoubleNode {

// Link to the next DoubleNode.
private DoubleNode next = null;
// Link to the previous DoubleNode.
private DoubleNode prev = null;
// The Movie data.
private Movie value = null;

/**
* Creates a new node with data and link to the previous and next nodes. Not
* copy safe as it accepts a reference to the data rather than a copy of the
* data.
*
* @param value
* the data to store in the node.
* @param next
* the previous node to link to.
* @param next
* the next node to link to.
*/
public DoubleNode(final Movie value, final DoubleNode prev,
   final DoubleNode next) {
   //your code here
}

/**
* Returns the next node in the linked structure.
*
* @return The node that follows this node. Must be copy safe.
*/
public final DoubleNode getNext() {
   //your code here
   return null;//you must change this statement as per your requirement
}

/**
* Returns the previous node in the linked structure.
*
* @return The node that precedes this node. Must be copy safe.
*/
public final DoubleNode getPrev() {
   //your code here
   return null;//you must change this statement as per your requirement
}

/**
* Returns the node data. Must be copy safe.
*
* @return The data portion of the node.
*/
public final Movie getValue() {
   //your code here
   return null;//you must change this statement as per your requirement
}

/**
* Links this node to the next node.
*
* @param next
* The new node to link to.
*/
public final void setNext(final DoubleNode next) {
   //your code here
}

/**
* Links this node to the previous node.
*
* @param prev
* The new node to link to.
*/
public final void setPrev(final DoubleNode prev) {
   //your code here
}
}

Answer 1

Please find below the testing code snippet fron the operations on doubly linked list along with the sample output:

Please find POJO for movie which was necessary for the completion of code :

---------------------------------------------------------------------------

Movie.java

public class Movie {
   private int movieId;
   private String name;
   public int getMovieId() {
       return movieId;
   }
   public void setMovieId(int movieId) {
       this.movieId = movieId;
   }
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public Movie(int movieId, String name) {
       super();
       this.movieId = movieId;
       this.name = name;
   }
   @Override
   public String toString() {
       return "Movie [movieId=" + movieId + ", name=" + name + "]";
   }
  

}
-------------------------------------------------------------------------------

DoubleNode.java

package org.bnymellon.js;

/**
* The individual node for a double-linked structure where movies are stored *
* objects. This is a double-linked node. The node link can be updated, * but
* not node data to prevent data moving between nodes. * Data structures must be
* rearranged by moving nodes.
*
* @author
* @version 2010-10-09
*/
public final class DoubleNode {

// Link to the next DoubleNode.
   private DoubleNode next = null;
// Link to the previous DoubleNode.
   private DoubleNode prev = null;
// The Movie data.
   private Movie value = null;

   /**
   * Creates a new node with data and link to the previous and next nodes. Not
   * copy safe as it accepts a reference to the data rather than a copy of the
   * data.
   *
   * @param value the data to store in the node.
   * @param next the previous node to link to.
   * @param next the next node to link to.
   */
   public DoubleNode(final Movie value, final DoubleNode prev, final DoubleNode next) {
       this.next = next;
       this.prev = prev;
       this.value = value;
   }

   /**
   * Returns the next node in the linked structure.
   *
   * @return The node that follows this node. Must be copy safe.
   */
   public final DoubleNode getNext() {
       return this.next;
   }

   /**
   * Returns the previous node in the linked structure.
   *
   * @return The node that precedes this node. Must be copy safe.
   */
   public final DoubleNode getPrev() {
       return this.prev;
      
   }

   /**
   * Returns the node data. Must be copy safe.
   *
   * @return The data portion of the node.
   */
   public final Movie getValue() {
       return this.value;
   }

   /**
   * Links this node to the next node.
   *
   * @param next The new node to link to.
   */
   public final void setNext(final DoubleNode next) {
       if(this.next == null) {
           this.next = next;
           next.next = null;
           next.prev = this;
       }else {
           next.next = this.next;
           next.prev = this;
           this.next.prev = next;
           this.next = next;
       }
      
   }

   /**
   * Links this node to the previous node.
   *
   * @param prev The new node to link to.
   */
   public final void setPrev(final DoubleNode prev) {
       if(prev.prev == null) {
           this.prev = prev;
           prev.next = this;
           prev.prev = null;
       }else {
           this.prev.next = prev;
           prev.prev = this.prev;
           this.prev = prev;
           prev.next = this;
       }
   }
}

------------------------------------------------------------------------------------------

DoubleLink.java

package org.bnymellon.js;

public class DoubleLink {

   // First node of double linked list

   private DoubleNode head = null;

   // Number of elements currently stored in linked list

   private int length = 0;

   // Last node of double linked list.

   private DoubleNode last = null;

   /**
   *
   * Adds a new Movie element to the list at the head position
   *
   * before the previous head, if any. Increments the length of the List.
   *
   *
   *
   * @param value
   *
   * The value to be added at the head of the list.
   *
   *
   *
   * @return true if node is added successfully, else false.
   *
   */

   public final boolean addNode(final Movie value) {
       try {
           DoubleNode temp = new DoubleNode(value, null, null);
           if(head ==null ) {
               head = temp;
               last = head;
           }else {
               this.head.setPrev(temp);              
           }
           this.head = temp;
           this.length++;
           return true;
       }catch(Exception e) {
           e.printStackTrace();
           return false;
       }

   }

   /**
   *
   * Removes the value at the front of this List.
   *
   *
   *
   * @return The value at the front of this List.
   *
   */

   public Movie removeFront() {
       DoubleNode front = this.head;
       this.head = this.head.getNext();
       this.length--;
       return front.getValue();
   }

   /**
   *
   * Returns the head element in the linked structure. Must be copy safe.
   *
   *
   *
   * @return the head node.
   *
   */

   public final DoubleNode getHead() {

       return this.head;
   }

   /**
   *
   * Returns the current number of elements in the linked structure.
   *
   *
   *
   * @return the value of length.
   *
   */

   public final int getLength() {

       return this.length;

   }

   /**
   *
   * Returns the last node in the linked structure. Must be copy safe.
   *
   *
   *
   * @return the last node.
   *
   */

   public final DoubleNode getLast() {

       return this.last;

   }

   /**
   *
   * Determines whether the double linked list is empty or not.
   *
   *
   *
   * @return true if list is empty, false otherwise.
   *
   */

   public final boolean isEmpty() {

       if(this.length == 0) {
           return true;
       }else {
           return false;
       }

   }

   /**
   *
   * Returns all the data in the list in the form of an array.
   *
   *
   *
   * @return The array of Movie elements. Must be copy safe
   *
   */

   public final Movie[] toArray() {
       Movie[] returnArr = new Movie[this.length];
       DoubleNode curr = this.head;
       int i=0;
       while(curr!=null) {
           returnArr[i] = curr.getValue();
           curr = curr.getNext();
           i++;
       }
       return returnArr;

   }
}