CS 535: Object-Oriented Programming & Design

1. References
2. Problem 3 - Linked List
   1. One(?) Abstraction Solution
   2. The Two in One Solution
   3. What to do with Node?
   4. How to Go through each element of the list
   5. toString Issues
   6. Giving the Node Some More Intelligence
   7. Issues and Comments

Doc 15, Comments on Assignment 1, part 2 Slide # 1

class Node
   {
   int element;
   Node next;
   }

class Test
   {
   public  static  void  main( String  args[] ) 
      {
      prompt user for input
      create nodes
      link nodes
      count sum
      compute average
      }
   }

Doc 15, Comments on Assignment 1, part 2 Slide # 2

class Node
   {
   int element;
   Node next = null;
   Node front;
   static int nodeCount;
   
   public void prepend( int data )
      { 
      Node newElement = new Node();
      newElement.element = data;
      newElement.next = next;
      front = this;
      nodeCount++;
      }
   
   public int size()
      {
      return nodeCount;
      }
   
   //other methods not shown
   }

Doc 15, Comments on Assignment 1, part 2 Slide # 3

class Node
   {
   int element;
   Node next;
   }

class Node
   {
   private int data;
   private Node next = null;
   
   public void setNext( Node aNode )
      {
      aNode.next = next;
      next = aNode;
      }
      
   public Node getNext()
      {
      return next;
      }

   public void setData( int newData )
      {
      data = newData;
      }
      
   public int getData()
      {
      return data;
      }
   }
Doc 15, Comments on Assignment 1, part 2 Slide # 4

class Node
   {
   int data;
   Node next = null;

   public Node( int initialData, Node nextInList )
      {
      data = initialData;
      next = nextInList;
      }   
   }
   
public class LinkedList
   {
   final static Node END_OF_LIST = null;
   
   private Node front = END_OF_LIST;
   private int nodeCount = 0;
   
   public void prepend( int data )
      {
      front = new Node( data, front );
      nodeCount++;
      }
   }
Doc 15, Comments on Assignment 1, part 2 Slide # 5

class LinkedListEnumeration implements Enumeration
   {
   private Node nextNode;
   
   public LinkedListEnumeration( LinkedList aList )
      {
      nextNode = aList.front;
      }
   
   public boolean hasMoreElements()
      {
      if (nextNode == LinkedList.END_OF_LIST )
         return false;
      else
         return true;
      } 
      
   public Object nextElement()
      {
      int data = nextNode.data;
      nextNode = nextNode.next;
      return  new Integer( data );
      }
   }

Doc 15, Comments on Assignment 1, part 2 Slide # 6

public class LinkedList
   {
   final static Node END_OF_LIST = null;
   
   Node front = END_OF_LIST;
   private int nodeCount = 0;
   
   public void prepend( int data )
      {
      front = new Node( data, front );
      nodeCount++;
      }
   
   public Enumeration elements()
      {
      return new LinkedListEnumeration( this );
      }
   
   public int size()
      {
      return nodeCount;
      }

Doc 15, Comments on Assignment 1, part 2 Slide # 7

   public String toString()
      {
      StringBuffer stringifiedList = new StringBuffer( size() * 2);
      Enumeration list = elements();

      stringifiedList.append( "LinkedList(");
      
      while ( list.hasMoreElements() )
         {
         stringifiedList.append( list.nextElement() );
         stringifiedList.append( ", ");
         }
         
      // added one too many ", ", so remove last one
      stringifiedList.setLength( stringifiedList.length() -2 );
      
      stringifiedList.append( ")");
      return       stringifiedList.toString();
      }
   }

class Test
   {
   public  static  void  main( String  args[] ) 
      {
      LinkedList sample = new LinkedList();
      sample.prepend( 4 );
      sample.prepend( 3 );
      sample.prepend( 2 );
      sample.prepend( 1 );
      System.out.println( sample );
      }
   }
Doc 15, Comments on Assignment 1, part 2 Slide # 8

• * toString method does not use links!

Went every you need to traverse the list use the enumeration

• * I did not perform any IO in the toString method

• * If list is very long, toString() will consume lots of memory

For now we can limit the number of items that toString returns

Will see later (use stream/writer) how to deal with long lists.

Doc 15, Comments on Assignment 1, part 2 Slide # 9

class Node
   {
   protected int data;
   protected Node next = null;
   protected Node previous = null;

   public Node( int initialData, 
                     Node previousInList, 
                     Node nextInList )
      {
      data = initialData;
      next = nextInList;
      previous = previousInList;
      }
   
   public void append( int data)
      {
      next = new Node( data, this, next);
      }

   public void append( Node newNode)
      {
      newNode.previous = this;
      newNode.next = next;
      next = newNode;
      }

   public void prepend( int data)
      {
      previous = new Node( data, previous, this);
      }

Doc 15, Comments on Assignment 1, part 2 Slide # 10

   public void prepend( Node newNode)
      {
      newNode.previous = previous;
      newNode.next = this;
      previous = newNode;
      }
   
   public void remove()
      {
      previous.next = next;
      next.previous = previous;
      }
      
   public int getData()
      {
      return data;
      }
   
   public void setData( int newData )
      {
      data = newData;
      }
   }
Doc 15, Comments on Assignment 1, part 2 Slide # 11

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