Question

Complete two of the List methods: SinglyLinkedList::size() and SinglyLinkedList::get().

import java.util.AbstractList;


public class SinglyLinkedList<E> extends AbstractList<E> {

  /** Reference to the first node in our linked list. This will be null if the list is empty. */
  private Entry head;

  /**
   * Creates an empty list.
   */
  public SinglyLinkedList() {
    reset();
  }

  /**
   * This method, which is only used within the SinglyLinkedList class, returns the instance to its initial state. This
   * call will reset the head to be null, which also empties the linked list.
   */
  private void reset() {
    head = null;
  }

  /**
   * Returns the element at the specified index in this list.
   *
   * @param index List location whose element should be returned.
   * @return Element at the specified index in this list
   */
  @Override
  public E get(int index) {

  }

  /**
   * Returns the number of elements currently in this list.
   *
   * @return the number of elements in the list
   */
  @Override
  public int size() {

  }

  /**
   * Class which defines the Entry instances ("nodes") in this single-linked-based list. Note that this class does not
   * specify a generic type, because it MUST be identical to the element type of the main class.
   *
   * @author Matthew Hertz
   */
  private class Entry {
    /** Element stored with the current entry. */
    private E element;

    /** Reference to the next entry in our linked list or null if this is the final link. */
    private Entry next;

    /** Create a new, blank Entry. */
    public Entry() {
      element = null;
      next = null;
    }
  }
}

Answer 1

Please find my implementation.

package year_2017.october.thirdweek;

import java.util.AbstractList;

public class SinglyLinkedList<E> extends AbstractList<E> {

   /** Reference to the first node in our linked list. This will be null if the list is empty. */

   private Entry head;

   /**

   * Creates an empty list.

   */

   public SinglyLinkedList() {

       reset();

   }

   /**

   * This method, which is only used within the SinglyLinkedList class, returns the instance to its initial state. This

   * call will reset the head to be null, which also empties the linked list.

   */

   private void reset() {

       head = null;

   }

   /**

   * Returns the element at the specified index in this list.

   *

   * @param index List location whose element should be returned.

   * @return Element at the specified index in this list

   */

   @Override

   public E get(int index) {

       if(index < 0 || index >= size())

           return null;

      

       int i = 0;

       Entry temp = head;

       while(i < index) {

           i++;

           temp = temp.next;

       }

      

       return temp.element;

   }

   /**

   * Returns the number of elements currently in this list.

   *

   * @return the number of elements in the list

   */

   @Override

   public int size() {

       int i = 0;

       Entry temp = head;

       while(temp != null) {

           i++;

           temp = temp.next;

       }

       return i;

   }

   /**

   * Class which defines the Entry instances ("nodes") in this single-linked-based list. Note that this class does not

   * specify a generic type, because it MUST be identical to the element type of the main class.

   *

   * @author Matthew Hertz

   */

   private class Entry {

       /** Element stored with the current entry. */

       private E element;

       /** Reference to the next entry in our linked list or null if this is the final link. */

       private Entry next;

       /** Create a new, blank Entry. */

       public Entry() {

           element = null;

           next = null;

       }

   }

}