ListClass.java

package rene.util.list;

/**
 * A class for a list of things. The list is forward and backward chained.
 * 
 * @see rene.list.ListElement
 */

public class ListClass
{
	ListElement First, Last; // Pointer to start and end of list.

	/**
	 * Generate an empty list.
	 */
	public ListClass ()
	{
		First = null;
		Last = null;
	}

	/**
	 * Append a node to the list
	 */
	public void append (ListElement l)
	{
		if (Last == null)
			init(l);
		else
		{
			Last.next(l);
			l.previous(Last);
			Last = l;
			l.next(null);
			l.list(this);
		}
	}

	public void prepend (ListElement l)
	// prepend a node to the list
	{
		if (First == null)
			init(l);
		else
		{
			First.previous(l);
			l.next(First);
			First = l;
			l.previous(null);
			l.list(this);
		}
	}

	/*
	 * @param l ListElement to be inserted.
	 * 
	 * @param after If null, it works like prepend.
	 */
	public void insert (ListElement l, ListElement after)
	{
		if (after == Last)
			append(l);
		else if (after == null)
			prepend(l);
		else
		{
			after.next().previous(l);
			l.next(after.next());
			after.next(l);
			l.previous(after);
			l.list(this);
		}
	}

	/**
	 * initialize the list with a single element.
	 */
	public void init (ListElement l)
	{
		Last = First = l;
		l.previous(null);
		l.next(null);
		l.list(this);
	}

	/**
	 * Remove a node from the list. The node really should be in the list, which
	 * is not checked.
	 */
	public void remove (ListElement l)
	{
		if (First == l)
		{
			First = l.next();
			if (First != null)
				First.previous(null);
			else Last = null;
		}
		else if (Last == l)
		{
			Last = l.previous();
			if (Last != null)
				Last.next(null);
			else First = null;
		}
		else
		{
			l.previous().next(l.next());
			l.next().previous(l.previous());
		}
		l.next(null);
		l.previous(null);
		l.list(null);
	}

	/**
	 * Empty the list.
	 */
	public void removeall ()
	{
		First = null;
		Last = null;
	}

	/** remove everything after e */
	public void removeAfter (ListElement e)
	{
		e.next(null);
		Last = e;
	}

	/**
	 * @return First ListElement.
	 */
	public ListElement first ()
	{
		return First;
	}

	/**
	 * @return Last ListElement.
	 */
	public ListElement last ()
	{
		return Last;
	}

	/**
	 * Prints the class
	 */
	@Override
	public String toString ()
	{
		ListElement e = First;
		String s = "";
		while (e != null)
		{
			s = s + e.content().toString() + ", ";
			e = e.next();
		}
		return s;
	}

}