In this homework problem we’ll begin completing an implementation of SimpleList that uses a linked list of Item objects internally. We’ve provided some starter code in a class called SimpleLinkedList. However, the get and set methods rely on a helper function called getItem to work properly, which is not properly implemented yet. You should create a class called YourSimpleLinkedList that inherits from SimpleLinkedList and provide a correct implementation of getItem. getItem should return a reference to the Item at that position in the list, or null if no such item exists. You may want to look at the implementation of size in SimpleLinkedList for a reminder of how to walk a linked list using a for loop. You will also need to provide a constructor for YourSimpleLinkedList that takes an array of Object references and simply passes them to a call to super to properly initialize SimpleLinkedList. A portion of the implementation of SimpleLinkedList follows:

The solution contains multiple java files. The initial linked list is 10 20 30 40 . The modified list is 20 30 40

Explanation

//Define the interface SimpleList;

public interface SimpleList

{

   public Object get (int index);

   public void set (int index, Object element);

   public void add (int index, Object element);

   public Object remove(int index);

   public int size();

}

SimpleLinkedList.java:

//Define the class SimpleLinkedList that implements the SimpleList.

public class SimpleLinkedList implements SimpleList

{

   //Define the Item class.

   class Item

   {

       Object value;

       Item next;          

       Item (Object setValue, Item setNext)

       {

           value = setValue;

           next = setNext;

       }

   }      

   protected Item start;

   protected int currentSize;      

   //Define the default constructor.

   public SimpleLinkedList()

   {

       currentSize = 0;

       start = null;

   }      

   //Define the parameterized constructor.

   SimpleLinkedList(Object[] values)

   {

       currentSize = 0;          

       //Start the loop and call the add method.

       for(int i = 0; i<values.length;i++)

       {

           add(i, values[i]);

       }

   }      

   //Define the method to return the object

   // at the given index.

   atOverride

   public Object get (int index)

   {

       //Call the getItem() method and return it's value.

       return getItem(index).value;

   }      

   //Define the set() method.

   atOverride

   public void set (int index, Object element)

   {

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

       {

           return;

       }

       int currentIndex = 0;          

       for (Item current = start; current != null; current = current.next)

       {

           if (currentIndex == index)

           {

               current.value = element;

               break;

           }

           currentIndex++;

       }

   }    

   //Define the getItem() method.

   protected Item getItem(int index)

   {

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

       {

           return null;

       }      

       int currentIndex = 0;        

       for (Item current = start; current != null; current = current.next)

       {

           if (currentIndex == index)

           {

               return current;

           }

           currentIndex++;

       }

       return null;

   }      

   //Define the add() method.

   atOverride

   public void add (int index, Object toAdd)

   {

       if (index == 0)

       {

           start = new Item (toAdd, start);

           currentSize++;

           return;

       }        

       Item previousItem = getItem(index - 1);        

       if(previousItem == null)

       {

           return;

       }          

       Item newItem = new Item(toAdd, previousItem.next);

       previousItem.next = newItem;

       currentSize++;

   }      

   //Define the method to return the size of the linked list.

   atOverride

   public int size ()

   {

       return currentSize;

   }      

   //Define the method to remove an index from the linked list.

   atOverride

   public Object remove (int index) {

       // TODO Auto-generated method stub

       return null;

   }      

}

YourSimpleLinkedList.java:

//Define the YourSimpleLinkedList class.

public class YourSimpleLinkedList extends SimpleLinkedList

{

   //Define the default constructor.s

   public YourSimpleLinkedList()

   {

       super();

   }      

   //Define the parameterized constructor.

   YourSimpleLinkedList(Object[] values)

   {

       super(values);

   }

   //Define the method to remove an index.

   at Override

   public Object remove(int index)

   {

       //Return null if the index is out of range.

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

       {

           return null;

       }        

       //Set the start Item if the first value

       // is to be removed.

       if (index == 0)

       {

           //Store the value of the node to be removed.

           Object temp = start.value;

           //Set the start Item.

           start = start.next;

           //Update the size of the linked list and return

           // the deleted value.

           currentSize--;

           return temp;

       }        

       //Initialize the required variables.

       int currentIndex = 0;

       Item current = start;

       Item prev = start;        

       //Start the loop to traverse the list.

       while (current != null)

       {

           //Check the index value.

           if (currentIndex == index)

           {

               //Store the value to be deleted.

               Object temp = current.value;                

               //Set the next pointer.

               prev.next = current.next;                  

               //Update the size of the linked list and return

               // the deleted value.

               currentSize--;

               return temp;

           }            

           //Update the values.

           currentIndex++;

           prev = current;

           current = current.next;

       }

       return null;

   }

}

Main.java:

public class Main

{

   public static void main(String[] args)

   {

       //Create a list of objects.

       Object [] values = {10, 20, 30, 40};          

       //Create an object of the YourSimpleLinkedList class.

       YourSimpleLinkedList myList = new YourSimpleLinkedList(values);        

       //Display the initial list.

       System.out.print("The initial linked list is ");

       for (int i=0;i<myList.size();i++)

       {

           System.out.print(myList.get(i) + " ");

       }        

       //Remove an index from the list.

       myList.remove(0);        

       //Display the modified list.

       System.out.println();

       System.out.print("The modified list is ");

       for (int i=0;i<myList.size();i++)

       {

           System.out.print(myList.get(i) + " ");

       }

   }  

}

sure

Explanation:

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