Initial revision

ListException.java

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+
+public class ListException extends RuntimeException
+{
+  public ListException(String s) 
+  {
+    super(s);
+  }  // end constructor
+}  // end ListException

ListSortedInterface.java

@@ -0,0 +1,59 @@
+/*	Andrew Coleman
+	CSC-2020 10:00 AM
+*/
+
+import java.util.Iterator;
+
+public interface ListSortedInterface	{
+	/**
+	 *  Checks to see if the list is empty and returns a boolean value. <BR>
+	 *  Preconditions: none. 
+	 *  Postconditions: Returns true if empty, false if it is not empty. 
+	 */
+	public boolean isEmpty();
+
+	/**
+	 *  Returns the current size of the list. <BR>
+	 *  Preconditions: none. 
+	 *  Postconditions: Returns an interger of the size. 
+	 */
+	public int size();
+
+	/**
+	 *  Adds a Comparable item to the list. <BR>
+	 *  Preconditions: Requires a Comparable item to insert into the list. 
+	 *  Postconditions: Inserts the Comparable item in the list. 
+	 *  Throws: Throws a ListException if you try and add a duplicate entry into the list. 
+	 */
+	public void add(Comparable item) throws ListException;
+
+	/**
+	 *  Removes an item from the list. <BR>
+	 *  Preconditions: Requires a Comparable item to remove. 
+	 *  Postconditions: Removes the item from the list. 
+	 *  Throws: Throws a ListException if the item is not found.
+	 */
+	public void remove(Comparable item) throws ListException;
+
+	/**
+	 *  Returns an item in the list at the specified index. <BR>
+	 *  Preconditions: A valid integer index value. 
+	 *  Postconditions: Returns a Comparable object at the said index. 
+	 *  Throws: Throws a ListException if the index value is out of range. 
+	 */
+	public Comparable get(int index) throws ListException;
+
+	/**
+	 *  Removes all entries in the list. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Removes all items in the list. 
+	 */
+	public void removeAll();
+
+	/**
+	 *  Creates an Iterator to cycle through the list. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Returns the Iterator for the list. 
+	 */
+	public Iterator iterator();
+}

ListSortedIterator.java

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+/*	Andrew Coleman
+	CSC-2020 10:00 AM
+*/
+
+import java.util.Iterator;
+
+public class ListSortedIterator implements Iterator	{
+	/** Index keeps the current position in the data collection and listsize the the size of the list (only used for error checking) */
+	private int index, listsize;
+
+	/** the collection of data */
+	private ListSortedInterface mylist;
+
+	/**
+	 *  Creates the Iterator for the specified list. <BR>
+	 *  Preconditions: An object that implements the ListSortedInterface. 
+	 *  Postconditions: none.
+	 */
+	public ListSortedIterator (ListSortedInterface list)	{
+		index = 1;
+		listsize = list.size();
+		mylist = list;
+	}
+
+	/**
+	 *  Resets all private integer values in the object to defaults, ie when the collection changes. <BR>
+	 *  Preconditions: None.
+	 *  Postconditions: Defaults all private integer values. 
+	 */
+	private void reset ()	{
+		index = 1; listsize = mylist.size();
+	}
+
+	/**
+	 *  Determines if there are more objects in the collection. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Returns a boolean value true if there are more objects, false otherwise. 
+	 *  Throws: Throws a ListException if the data has been changed. 
+	 */
+	public boolean hasNext ()	{
+		if (listsize != mylist.size())	{
+			reset();
+			throw new ListException ("Changes have been made to the collection.");
+		}
+		return (index <= listsize);
+	}
+
+	/**
+	 *  Returns an Object at the current position in the collection. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Returns the current Object in the collection.
+	 *  Throws: Throws a ListException if the data has been changed, or if the end of the list has been reached. 
+	 */
+	public Object next ()	{
+		if (listsize != mylist.size())	{
+			reset ();
+			throw new ListException ("Changes have been made to the collection.");
+		}
+		if (index <= listsize)	{
+			index++;
+			return ((Object) mylist.get (index - 1));
+		}
+		else
+			throw new ListException ("End of collection has been reached.");
+	}
+
+	/**
+	 *  Removes the current item in the list. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Removes the current item from the list. 
+	 */
+	public void remove ()	{
+		mylist.remove (mylist.get (index));
+	}
+}

ListSortedReferenceBased.java

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+/*	Andrew Coleman
+	CSC-2020 10:00 AM
+*/
+
+import java.util.Iterator;
+
+public class ListSortedReferenceBased implements ListSortedInterface	{
+
+	/** The Node that points to the first item in the collection */
+	private Node head;
+
+	/** Keeps track of the current size of the collection */
+	private int size;
+
+	/**
+	 *  Sets up the instance variables to default values. <BR>
+	 *  Preconditions: None. 
+	 *  Postconditions: Sets the default values for the instance variables. 
+	 */
+	public ListSortedReferenceBased ()	{
+		head = null;
+		size = 0;
+	}
+
+	public boolean isEmpty ()	{
+		return (size == 0);
+	}
+
+	public int size ()	{
+		return size;
+	}
+
+	public void removeAll ()	{
+		head = null; size = 0;
+	}
+
+	public Iterator iterator ()	{
+		return new ListSortedIterator (this);
+	}
+
+	/**
+	 *  Finds the Node of a specified Comparable item. <BR>
+	 *  Preconditions: Requires a Comparable object. 
+	 *  Postconditions: Returns a Node of the item, null if it is not found.
+	 */
+	private Node find (Comparable item)	{
+		Node curr = head;
+		while (curr != null)	{
+			if ( ((Comparable) curr.getItem()).compareTo(item) == 0)
+				return curr;
+			curr = curr.getNext();
+		}
+		return null;
+	}
+
+	/**
+	 *  Finds the Node at the specified index in the collection. <BR>
+	 *  Preconditions: Assumes an integer in the valid range (1 - size()). 
+	 *  Postconditions: Returns the node at the index. 
+	 */
+	private Node find (int index)	{
+		Node curr = head;
+		for (int skip = 1; skip < index; skip++)
+			curr = curr.getNext();
+		return curr;
+	}
+
+	/**
+	 * Locates the last Node that is less than the passed Comparable object. <BR>
+	 * Preconditions: Requires a Comparable object, and assumes that size > 1.
+	 * Postconditions: Returns a Node directly before where the passed object should be in the collection, or null if it should be the first item. 
+	 */
+	private Node findplace (Comparable item)	{
+		/* curr will compare itself to item until it is too big, then prev is in the correct place */
+		Node curr = head.getNext(), prev = head;
+		/* must check to see if the first item is the item searched for */
+		if (((Comparable) prev.getItem()).compareTo(item) > 0)
+			return null;
+		/* while not at the end of the list and the item in curr is less than item */
+		while (curr != null && ((Comparable) curr.getItem()).compareTo(item) < 0)	{
+			prev = curr;
+			curr = curr.getNext();
+		}
+		return prev;
+	}
+
+	public void add (Comparable item) throws ListException	{
+		/* is item in the collection? */
+		if (find (item) == null)	{
+			/* curr will be the active Node in the collection */
+			Node curr = head;
+			/* temp will be the inserted Node */
+			Node temp;
+			/* if the list is empty, just put in temp */
+			if (size == 0)
+				head = new Node (item);
+			/* if the size of the collection is 1, then check to see if the Node is bigger or less */
+			else if (size == 1)	{
+				if ( ((Comparable) curr.getItem()).compareTo (item) > 0)	{
+					temp = new Node (item, head);
+					head = temp;
+				}
+				else	{
+					temp = new Node (item);
+					head.setNext(temp);
+				}
+			}
+			/* well, the collection must be > 1 so now use the nifty findplace and figure out the Node that temp should be placed after */
+			else	{
+				curr = findplace (item);
+				if (curr == null)
+					temp = new Node (item, head);
+				else {
+					temp = new Node (item, curr.getNext());
+					curr.setNext (temp);
+				}
+			}
+			/* increment the all important size */
+			size++;
+		}
+		else	{
+			/* use a variable and one throw rather than two different throws... less typing i suppose */
+			String s;
+			if (size == 0)
+				s = " or list is empty";
+			else
+				s = "";
+			throw new ListException ("Item is already in data collection" + s + ".");
+		}
+	}
+
+	public void remove (Comparable item) throws ListException	{
+		/* if the item is in fact in the collection */
+		if (find (item) == null)
+			throw new ListException ("Item is not in the data collection.");
+		else	{
+			/* if there is more than 2 objects in the collection then find the previous Node */
+			if (size > 2)	{
+				Node curr = findplace(item);
+				/* just skip over the item to remove */
+				curr.setNext (curr.getNext().getNext());
+			}
+			/* if the size is 2, then one or the other is the item in question */
+			else if (size == 2)	{
+				/* must cast... Node and Object only */
+				if (((Comparable) head.getItem()).compareTo(item) == 0)
+					head = head.getNext();
+				else
+					head.setNext(null);
+			}
+			/* if the size is 1, well, just remove it all */
+			else
+				head = null;
+			/* and they will all remove exactly 1, so 1 decrement for all cases */
+			size--;
+		}
+			
+	}
+
+	public Comparable get (int index) throws ListException	{
+		/* must check and see if index is within the range of the collection */
+		if (index > 0 && index <= size)	{
+			Node curr = head;
+			for (int skip = 1; skip < index; skip++)
+				curr = curr.getNext ();
+			/* must cast to Comparable since Node uses Object(s) */
+			return ((Comparable) curr.getItem());
+		}
+		else
+			throw new ListException ("Index is out of range.");
+	}
+
+	/**
+	 * Returns a string containing each Node separated by newlines. <BR>
+	 * Preconditions: None.
+	 * Postconditions: Returns a string containing an easy to read format of the collection. 
+	 */
+	public String toString ()	{
+		String result = "";
+		/* i save 1 line of code if i use the iterator, rather than looping through the list */
+		/* besides, i haven't used the iterator anywhere else */
+		Iterator allyourbase = iterator();
+		while (allyourbase.hasNext ())
+			result += allyourbase.next() + "\n";
+		return result;
+	}
+}

Node.java

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+public class Node	{
+	private Object item;
+	private Node next;
+
+	public Node (Object item)	{
+		this.item = item;
+		next = null;
+	}
+
+	public Node (Object item, Node next)	{
+		this.item = item;
+		this.next = next;
+	}
+
+	public void setItem (Object item)	{
+		this.item = item;
+	}
+
+	public void setNext (Node next)	{
+		this.next = next;
+	}
+
+	public Object getItem ()	{
+		return item;
+	}
+
+	public Node getNext ()	{
+		return next;
+	}
+}

drivertest.java

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+/*	Andrew Coleman
+	CSC-2020 10:00 AM
+*/
+
+public class drivertest	{
+	public static void main (String[] args)	{
+		ListSortedInterface list = new ListSortedReferenceBased();
+		try	{
+		list.add("b");
+		System.out.print(list + "\n\n");
+		list.add("a");
+		System.out.print(list + "\n\n");
+		list.add("d");
+		System.out.print(list + "\n\n");
+		list.add("c");
+		System.out.print(list + "\n\n");
+		list.remove("a");
+		System.out.print(list + "\n\n");
+		list.remove("d");
+		System.out.print(list + "\n\n");
+
+		System.out.println(list.get(2));
+		}
+		catch (ListException e)	{
+			System.out.println(e);
+		}
+	}
+}