doublylinkedlist.java

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//
// Copyright 2002 Nokia Mobile Phones Ltd.
//
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//
// Furthermore, information provided in this source code is preliminary,
// and may be changed substantially prior to final release. Nokia Mobile
// Phones Ltd. retains the right to make changes to this source code at
// any time, without notice. This source code is provided for informational
// purposes only.
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// source code. The licensee has the right to market, sell, distribute and
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package example.fireworks;


class DoublyLinkedList
{
    private final ListItem head = new ListItem();


    DoublyLinkedList()
    {
    }


    boolean isEmpty()
    {
        return head.next == null;
    }


    ListItem getFirst()
    {
        return head.next;
    }


    ListItem getNext(ListItem li)
    {
        if ((li.next == null) && (li.prev == null))
        {
            throw new IllegalArgumentException(
                "getNext from item not in list");
        }
        return li.next;
    }


    void remove(ListItem li)
    {
        li.remove();
    }


    void addFirst(ListItem li)
    {
        if ((li.next != null) || (li.prev != null))
        {
            throw new IllegalArgumentException(
                "addFirst item already in list");
        }
        li.next = head.next;
        if (li.next != null)
        {
            li.next.prev = li;
        }
        li.prev = head;
        head.next = li;
    }
}