mirror of git://gcc.gnu.org/git/gcc.git
957 lines
24 KiB
Java
957 lines
24 KiB
Java
/* LinkedList.java -- Linked list implementation of the List interface
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Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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import java.io.Serializable;
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import java.io.ObjectOutputStream;
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import java.io.ObjectInputStream;
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import java.io.IOException;
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import java.lang.reflect.Array;
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/**
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* Linked list implementation of the List interface. In addition to the
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* methods of the List interface, this class provides access to the first
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* and last list elements in O(1) time for easy stack, queue, or double-ended
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* queue (deque) creation. The list is doubly-linked, with traversal to a
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* given index starting from the end closest to the element.<p>
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*
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* LinkedList is not synchronized, so if you need multi-threaded access,
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* consider using:<br>
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* <code>List l = Collections.synchronizedList(new LinkedList(...));</code>
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* <p>
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*
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* The iterators are <i>fail-fast</i>, meaning that any structural
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* modification, except for <code>remove()</code> called on the iterator
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* itself, cause the iterator to throw a
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* {@link ConcurrentModificationException} rather than exhibit
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* non-deterministic behavior.
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*
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* @author Original author unknown
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* @author Bryce McKinlay
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* @author Eric Blake <ebb9@email.byu.edu>
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* @see List
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* @see ArrayList
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* @see Vector
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* @see Collections#synchronizedList(List)
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* @since 1.2
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* @status missing javadoc, but complete to 1.4
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*/
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public class LinkedList extends AbstractSequentialList
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implements List, Cloneable, Serializable
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{
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/**
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* Compatible with JDK 1.2.
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*/
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private static final long serialVersionUID = 876323262645176354L;
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/**
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* The first element in the list.
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*/
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transient Entry first;
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/**
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* The last element in the list.
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*/
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transient Entry last;
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/**
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* The current length of the list.
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*/
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transient int size = 0;
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/**
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* Class to represent an entry in the list. Holds a single element.
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*/
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private static final class Entry
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{
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/** The element in the list. */
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Object data;
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/** The next list entry, null if this is last. */
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Entry next;
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/** The previous list entry, null if this is first. */
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Entry previous;
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/**
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* Construct an entry.
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* @param data the list element
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*/
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Entry(Object data)
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{
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this.data = data;
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}
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} // class Entry
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/**
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* Obtain the Entry at a given position in a list. This method of course
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* takes linear time, but it is intelligent enough to take the shorter of the
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* paths to get to the Entry required. This implies that the first or last
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* entry in the list is obtained in constant time, which is a very desirable
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* property.
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* For speed and flexibility, range checking is not done in this method:
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* Incorrect values will be returned if (n < 0) or (n >= size).
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*
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* @param n the number of the entry to get
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* @return the entry at position n
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*/
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private Entry getEntry(int n)
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{
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Entry e;
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if (n < size / 2)
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{
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e = first;
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// n less than size/2, iterate from start
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while (n-- > 0)
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e = e.next;
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}
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else
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{
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e = last;
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// n greater than size/2, iterate from end
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while (++n < size)
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e = e.previous;
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}
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return e;
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}
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/**
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* Remove an entry from the list. This will adjust size and deal with
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* `first' and `last' appropriatly.
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*
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* @param e the entry to remove
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*/
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private void removeEntry(Entry e)
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{
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modCount++;
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size--;
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if (size == 0)
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first = last = null;
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else
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{
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if (e == first)
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{
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first = e.next;
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e.next.previous = null;
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}
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else if (e == last)
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{
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last = e.previous;
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e.previous.next = null;
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}
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else
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{
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e.next.previous = e.previous;
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e.previous.next = e.next;
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}
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}
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}
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/**
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* Checks that the index is in the range of possible elements (inclusive).
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*
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* @param index the index to check
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* @throws IndexOutOfBoundsException if index < 0 || index > size
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*/
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private void checkBoundsInclusive(int index)
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{
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if (index < 0 || index > size)
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throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
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+ size);
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}
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/**
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* Checks that the index is in the range of existing elements (exclusive).
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*
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* @param index the index to check
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* @throws IndexOutOfBoundsException if index < 0 || index >= size
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*/
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private void checkBoundsExclusive(int index)
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{
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if (index < 0 || index >= size)
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throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
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+ size);
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}
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/**
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* Create an empty linked list.
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*/
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public LinkedList()
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{
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}
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/**
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* Create a linked list containing the elements, in order, of a given
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* collection.
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*
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* @param c the collection to populate this list from
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* @throws NullPointerException if c is null
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*/
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public LinkedList(Collection c)
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{
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addAll(c);
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}
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/**
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* Returns the first element in the list.
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*
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* @return the first list element
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* @throws NoSuchElementException if the list is empty
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*/
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public Object getFirst()
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{
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if (size == 0)
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throw new NoSuchElementException();
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return first.data;
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}
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/**
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* Returns the last element in the list.
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*
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* @return the last list element
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* @throws NoSuchElementException if the list is empty
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*/
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public Object getLast()
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{
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if (size == 0)
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throw new NoSuchElementException();
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return last.data;
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}
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/**
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* Remove and return the first element in the list.
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*
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* @return the former first element in the list
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* @throws NoSuchElementException if the list is empty
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*/
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public Object removeFirst()
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{
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if (size == 0)
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throw new NoSuchElementException();
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modCount++;
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size--;
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Object r = first.data;
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if (first.next != null)
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first.next.previous = null;
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else
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last = null;
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first = first.next;
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return r;
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}
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/**
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* Remove and return the last element in the list.
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*
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* @return the former last element in the list
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* @throws NoSuchElementException if the list is empty
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*/
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public Object removeLast()
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{
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if (size == 0)
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throw new NoSuchElementException();
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modCount++;
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size--;
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Object r = last.data;
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if (last.previous != null)
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last.previous.next = null;
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else
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first = null;
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last = last.previous;
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return r;
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}
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/**
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* Insert an element at the first of the list.
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*
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* @param o the element to insert
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*/
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public void addFirst(Object o)
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{
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Entry e = new Entry(o);
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modCount++;
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if (size == 0)
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first = last = e;
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else
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{
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e.next = first;
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first.previous = e;
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first = e;
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}
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size++;
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}
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/**
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* Insert an element at the last of the list.
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*
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* @param o the element to insert
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*/
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public void addLast(Object o)
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{
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addLastEntry(new Entry(o));
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}
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/**
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* Inserts an element at the end of the list.
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*
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* @param e the entry to add
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*/
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private void addLastEntry(Entry e)
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{
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modCount++;
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if (size == 0)
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first = last = e;
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else
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{
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e.previous = last;
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last.next = e;
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last = e;
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}
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size++;
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}
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/**
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* Returns true if the list contains the given object. Comparison is done by
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* <code>o == null ? e = null : o.equals(e)</code>.
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*
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* @param o the element to look for
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* @return true if it is found
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*/
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public boolean contains(Object o)
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{
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Entry e = first;
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while (e != null)
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{
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if (equals(o, e.data))
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return true;
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e = e.next;
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}
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return false;
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}
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/**
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* Returns the size of the list.
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*
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* @return the list size
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*/
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public int size()
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{
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return size;
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}
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/**
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* Adds an element to the end of the list.
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*
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* @param e the entry to add
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* @return true, as it always succeeds
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*/
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public boolean add(Object o)
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{
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addLastEntry(new Entry(o));
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return true;
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}
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/**
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* Removes the entry at the lowest index in the list that matches the given
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* object, comparing by <code>o == null ? e = null : o.equals(e)</code>.
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*
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* @param o the object to remove
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* @return true if an instance of the object was removed
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*/
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public boolean remove(Object o)
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{
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Entry e = first;
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while (e != null)
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{
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if (equals(o, e.data))
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{
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removeEntry(e);
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return true;
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}
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e = e.next;
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}
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return false;
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}
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/**
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* Append the elements of the collection in iteration order to the end of
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* this list. If this list is modified externally (for example, if this
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* list is the collection), behavior is unspecified.
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*
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* @param c the collection to append
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* @return true if the list was modified
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* @throws NullPointerException if c is null
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*/
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public boolean addAll(Collection c)
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{
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return addAll(size, c);
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}
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/**
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* Insert the elements of the collection in iteration order at the given
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* index of this list. If this list is modified externally (for example,
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* if this list is the collection), behavior is unspecified.
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*
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* @param c the collection to append
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* @return true if the list was modified
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* @throws NullPointerException if c is null
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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*/
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public boolean addAll(int index, Collection c)
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{
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checkBoundsInclusive(index);
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int csize = c.size();
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if (csize == 0)
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return false;
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Iterator itr = c.iterator();
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// Get the entries just before and after index. If index is at the start
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// of the list, BEFORE is null. If index is at the end of the list, AFTER
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// is null. If the list is empty, both are null.
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Entry after = null;
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Entry before = null;
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if (index != size)
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{
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after = getEntry(index);
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before = after.previous;
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}
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else
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before = last;
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// Create the first new entry. We do not yet set the link from `before'
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// to the first entry, in order to deal with the case where (c == this).
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// [Actually, we don't have to handle this case to fufill the
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// contract for addAll(), but Sun's implementation appears to.]
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Entry e = new Entry(itr.next());
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e.previous = before;
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Entry prev = e;
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Entry firstNew = e;
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// Create and link all the remaining entries.
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for (int pos = 1; pos < csize; pos++)
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{
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e = new Entry(itr.next());
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e.previous = prev;
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prev.next = e;
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prev = e;
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}
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// Link the new chain of entries into the list.
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modCount++;
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size += csize;
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prev.next = after;
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if (after != null)
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after.previous = e;
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else
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last = e;
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if (before != null)
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before.next = firstNew;
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else
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first = firstNew;
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return true;
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}
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/**
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* Remove all elements from this list.
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*/
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public void clear()
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{
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if (size > 0)
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{
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modCount++;
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first = null;
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last = null;
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size = 0;
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}
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}
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/**
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* Return the element at index.
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*
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* @param index the place to look
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* @return the element at index
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* @throws IndexOutOfBoundsException if index < 0 || index >= size()
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*/
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public Object get(int index)
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{
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checkBoundsExclusive(index);
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return getEntry(index).data;
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}
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/**
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* Replace the element at the given location in the list.
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*
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* @param index which index to change
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* @param o the new element
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* @return the prior element
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* @throws IndexOutOfBoundsException if index < 0 || index >= size()
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*/
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public Object set(int index, Object o)
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{
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checkBoundsExclusive(index);
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Entry e = getEntry(index);
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Object old = e.data;
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e.data = o;
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return old;
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}
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/**
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* Inserts an element in the given position in the list.
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*
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* @param index where to insert the element
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* @param o the element to insert
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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*/
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public void add(int index, Object o)
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{
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checkBoundsInclusive(index);
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Entry e = new Entry(o);
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if (index < size)
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{
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modCount++;
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Entry after = getEntry(index);
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e.next = after;
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e.previous = after.previous;
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if (after.previous == null)
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first = e;
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else
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after.previous.next = e;
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after.previous = e;
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size++;
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}
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else
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addLastEntry(e);
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}
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/**
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* Removes the element at the given position from the list.
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*
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* @param index the location of the element to remove
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* @return the removed element
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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*/
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public Object remove(int index)
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{
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checkBoundsExclusive(index);
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Entry e = getEntry(index);
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removeEntry(e);
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return e.data;
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}
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/**
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* Returns the first index where the element is located in the list, or -1.
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*
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* @param o the element to look for
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* @return its position, or -1 if not found
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*/
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public int indexOf(Object o)
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{
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int index = 0;
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Entry e = first;
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while (e != null)
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{
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if (equals(o, e.data))
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return index;
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index++;
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e = e.next;
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}
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return -1;
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}
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/**
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* Returns the last index where the element is located in the list, or -1.
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*
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* @param o the element to look for
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* @return its position, or -1 if not found
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*/
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public int lastIndexOf(Object o)
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{
|
|
int index = size - 1;
|
|
Entry e = last;
|
|
while (e != null)
|
|
{
|
|
if (equals(o, e.data))
|
|
return index;
|
|
index--;
|
|
e = e.previous;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
/**
|
|
* Obtain a ListIterator over this list, starting at a given index. The
|
|
* ListIterator returned by this method supports the add, remove and set
|
|
* methods.
|
|
*
|
|
* @param index the index of the element to be returned by the first call to
|
|
* next(), or size() to be initially positioned at the end of the list
|
|
* @throws IndexOutOfBoundsException if index < 0 || index > size()
|
|
*/
|
|
public ListIterator listIterator(int index)
|
|
{
|
|
checkBoundsInclusive(index);
|
|
return new LinkedListItr(index);
|
|
}
|
|
|
|
/**
|
|
* Create a shallow copy of this LinkedList (the elements are not cloned).
|
|
*
|
|
* @return an object of the same class as this object, containing the
|
|
* same elements in the same order
|
|
*/
|
|
public Object clone()
|
|
{
|
|
LinkedList copy = null;
|
|
try
|
|
{
|
|
copy = (LinkedList) super.clone();
|
|
}
|
|
catch (CloneNotSupportedException ex)
|
|
{
|
|
}
|
|
copy.clear();
|
|
copy.addAll(this);
|
|
return copy;
|
|
}
|
|
|
|
/**
|
|
* Returns an array which contains the elements of the list in order.
|
|
*
|
|
* @return an array containing the list elements
|
|
*/
|
|
public Object[] toArray()
|
|
{
|
|
Object[] array = new Object[size];
|
|
Entry e = first;
|
|
for (int i = 0; i < size; i++)
|
|
{
|
|
array[i] = e.data;
|
|
e = e.next;
|
|
}
|
|
return array;
|
|
}
|
|
|
|
/**
|
|
* Returns an Array whose component type is the runtime component type of
|
|
* the passed-in Array. The returned Array is populated with all of the
|
|
* elements in this LinkedList. If the passed-in Array is not large enough
|
|
* to store all of the elements in this List, a new Array will be created
|
|
* and returned; if the passed-in Array is <i>larger</i> than the size
|
|
* of this List, then size() index will be set to null.
|
|
*
|
|
* @param a the passed-in Array
|
|
* @return an array representation of this list
|
|
* @throws ArrayStoreException if the runtime type of a does not allow
|
|
* an element in this list
|
|
* @throws NullPointerException if a is null
|
|
*/
|
|
public Object[] toArray(Object[] a)
|
|
{
|
|
if (a.length < size)
|
|
a = (Object[]) Array.newInstance(a.getClass().getComponentType(), size);
|
|
else if (a.length > size)
|
|
a[size] = null;
|
|
Entry e = first;
|
|
for (int i = 0; i < size; i++)
|
|
{
|
|
a[i] = e.data;
|
|
e = e.next;
|
|
}
|
|
return a;
|
|
}
|
|
|
|
/**
|
|
* Serializes this object to the given stream.
|
|
*
|
|
* @param s the stream to write to
|
|
* @throws IOException if the underlying stream fails
|
|
* @serialData the size of the list (int), followed by all the elements
|
|
* (Object) in proper order
|
|
*/
|
|
private void writeObject(ObjectOutputStream s) throws IOException
|
|
{
|
|
s.defaultWriteObject();
|
|
s.writeInt(size);
|
|
Entry e = first;
|
|
while (e != null)
|
|
{
|
|
s.writeObject(e.data);
|
|
e = e.next;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Deserializes this object from the given stream.
|
|
*
|
|
* @param s the stream to read from
|
|
* @throws ClassNotFoundException if the underlying stream fails
|
|
* @throws IOException if the underlying stream fails
|
|
* @serialData the size of the list (int), followed by all the elements
|
|
* (Object) in proper order
|
|
*/
|
|
private void readObject(ObjectInputStream s)
|
|
throws IOException, ClassNotFoundException
|
|
{
|
|
s.defaultReadObject();
|
|
int i = s.readInt();
|
|
while (--i >= 0)
|
|
addLastEntry(new Entry(s.readObject()));
|
|
}
|
|
|
|
/**
|
|
* A ListIterator over the list. This class keeps track of its
|
|
* position in the list and the two list entries it is between.
|
|
*
|
|
* @author Original author unknown
|
|
* @author Eric Blake <ebb9@email.byu.edu>
|
|
*/
|
|
private final class LinkedListItr implements ListIterator
|
|
{
|
|
/** Number of modifications we know about. */
|
|
private int knownMod = modCount;
|
|
|
|
/** Entry that will be returned by next(). */
|
|
private Entry next;
|
|
|
|
/** Entry that will be returned by previous(). */
|
|
private Entry previous;
|
|
|
|
/** Entry that will be affected by remove() or set(). */
|
|
private Entry lastReturned;
|
|
|
|
/** Index of `next'. */
|
|
private int position;
|
|
|
|
/**
|
|
* Initialize the iterator.
|
|
*
|
|
* @param index the initial index
|
|
*/
|
|
LinkedListItr(int index)
|
|
{
|
|
if (index == size)
|
|
{
|
|
next = null;
|
|
previous = last;
|
|
}
|
|
else
|
|
{
|
|
next = getEntry(index);
|
|
previous = next.previous;
|
|
}
|
|
position = index;
|
|
}
|
|
|
|
/**
|
|
* Checks for iterator consistency.
|
|
*
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
private void checkMod()
|
|
{
|
|
if (knownMod != modCount)
|
|
throw new ConcurrentModificationException();
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the next element.
|
|
*
|
|
* @return the next index
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public int nextIndex()
|
|
{
|
|
checkMod();
|
|
return position;
|
|
}
|
|
|
|
/**
|
|
* Returns the index of the previous element.
|
|
*
|
|
* @return the previous index
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public int previousIndex()
|
|
{
|
|
checkMod();
|
|
return position - 1;
|
|
}
|
|
|
|
/**
|
|
* Returns true if more elements exist via next.
|
|
*
|
|
* @return true if next will succeed
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public boolean hasNext()
|
|
{
|
|
checkMod();
|
|
return (next != null);
|
|
}
|
|
|
|
/**
|
|
* Returns true if more elements exist via previous.
|
|
*
|
|
* @return true if previous will succeed
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public boolean hasPrevious()
|
|
{
|
|
checkMod();
|
|
return (previous != null);
|
|
}
|
|
|
|
/**
|
|
* Returns the next element.
|
|
*
|
|
* @return the next element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws NoSuchElementException if there is no next
|
|
*/
|
|
public Object next()
|
|
{
|
|
checkMod();
|
|
if (next == null)
|
|
throw new NoSuchElementException();
|
|
position++;
|
|
lastReturned = previous = next;
|
|
next = lastReturned.next;
|
|
return lastReturned.data;
|
|
}
|
|
|
|
/**
|
|
* Returns the previous element.
|
|
*
|
|
* @return the previous element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws NoSuchElementException if there is no previous
|
|
*/
|
|
public Object previous()
|
|
{
|
|
checkMod();
|
|
if (previous == null)
|
|
throw new NoSuchElementException();
|
|
position--;
|
|
lastReturned = next = previous;
|
|
previous = lastReturned.previous;
|
|
return lastReturned.data;
|
|
}
|
|
|
|
/**
|
|
* Remove the most recently returned element from the list.
|
|
*
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws IllegalStateException if there was no last element
|
|
*/
|
|
public void remove()
|
|
{
|
|
checkMod();
|
|
if (lastReturned == null)
|
|
throw new IllegalStateException();
|
|
|
|
// Adjust the position to before the removed element, if the element
|
|
// being removed is behind the cursor.
|
|
if (lastReturned == previous)
|
|
position--;
|
|
|
|
next = lastReturned.next;
|
|
previous = lastReturned.previous;
|
|
removeEntry(lastReturned);
|
|
knownMod++;
|
|
|
|
lastReturned = null;
|
|
}
|
|
|
|
/**
|
|
* Adds an element between the previous and next, and advance to the next.
|
|
*
|
|
* @param o the element to add
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
*/
|
|
public void add(Object o)
|
|
{
|
|
checkMod();
|
|
modCount++;
|
|
knownMod++;
|
|
size++;
|
|
position++;
|
|
Entry e = new Entry(o);
|
|
e.previous = previous;
|
|
e.next = next;
|
|
|
|
if (previous != null)
|
|
previous.next = e;
|
|
else
|
|
first = e;
|
|
|
|
if (next != null)
|
|
next.previous = e;
|
|
else
|
|
last = e;
|
|
|
|
previous = e;
|
|
lastReturned = null;
|
|
}
|
|
|
|
/**
|
|
* Changes the contents of the element most recently returned.
|
|
*
|
|
* @param o the new element
|
|
* @throws ConcurrentModificationException if the list was modified
|
|
* @throws IllegalStateException if there was no last element
|
|
*/
|
|
public void set(Object o)
|
|
{
|
|
checkMod();
|
|
if (lastReturned == null)
|
|
throw new IllegalStateException();
|
|
lastReturned.data = o;
|
|
}
|
|
} // class LinkedListItr
|
|
}
|