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230 lines
8.9 KiB
Java
230 lines
8.9 KiB
Java
/* AbstractSequentialList.java -- List implementation for sequential access
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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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/**
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* Abstract superclass to make it easier to implement the List interface when
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* backed by a sequential-access store, such as a linked list. For random
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* access data, use AbstractList. This class implements the random access
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* methods (<code>get</code>, <code>set</code>, <code>add</code>, and
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* <code>remove</code>) atop the list iterator, opposite of AbstractList's
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* approach of implementing the iterator atop random access.
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* <p>
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*
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* To implement a list, you need an implementation for <code>size()</code>
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* and <code>listIterator</code>. With just <code>hasNext</code>,
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* <code>next</code>, <code>hasPrevious</code>, <code>previous</code>,
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* <code>nextIndex</code>, and <code>previousIndex</code>, you have an
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* unmodifiable list. For a modifiable one, add <code>set</code>, and for
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* a variable-size list, add <code>add</code> and <code>remove</code>.
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* <p>
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*
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* The programmer should provide a no-argument constructor, and one that
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* accepts another Collection, as recommended by the Collection interface.
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* Unfortunately, there is no way to enforce this in Java.
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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 Collection
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* @see List
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* @see AbstractList
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* @see AbstractCollection
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* @see ListIterator
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* @see LinkedList
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* @since 1.2
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* @status updated to 1.4
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*/
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public abstract class AbstractSequentialList extends AbstractList
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{
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/**
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* The main constructor, for use by subclasses.
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*/
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protected AbstractSequentialList()
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{
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}
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/**
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* Returns a ListIterator over the list, starting from position index.
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* Subclasses must provide an implementation of this method.
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*
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* @param index the starting position of the list
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* @return the list iterator
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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*/
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public abstract ListIterator listIterator(int index);
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/**
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* Insert an element into the list at a given position (optional operation).
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* This shifts all existing elements from that position to the end one
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* index to the right. This version of add has no return, since it is
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* assumed to always succeed if there is no exception. This iteration
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* uses listIterator(index).add(o).
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*
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* @param index the location to insert the item
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* @param o the object to insert
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* @throws UnsupportedOperationException if this list does not support the
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* add operation
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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* @throws ClassCastException if o cannot be added to this list due to its
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* type
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* @throws IllegalArgumentException if o cannot be added to this list for
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* some other reason
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*/
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public void add(int index, Object o)
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{
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listIterator(index).add(o);
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}
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/**
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* Insert the contents of a collection into the list at a given position
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* (optional operation). Shift all elements at that position to the right
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* by the number of elements inserted. This operation is undefined if
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* this list is modified during the operation (for example, if you try
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* to insert a list into itself).
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* <p>
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*
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* This implementation grabs listIterator(index), then proceeds to use add
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* for each element returned by c's iterator. Sun's online specs are wrong,
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* claiming that this also calls next(): listIterator.add() correctly
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* skips the added element.
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*
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* @param index the location to insert the collection
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* @param c the collection to insert
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* @return true if the list was modified by this action, that is, if c is
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* non-empty
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* @throws UnsupportedOperationException if this list does not support the
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* addAll operation
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* @throws IndexOutOfBoundsException if index < 0 || index > size()
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* @throws ClassCastException if some element of c cannot be added to this
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* list due to its type
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* @throws IllegalArgumentException if some element of c cannot be added
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* to this list for some other reason
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* @throws NullPointerException if the specified collection is null
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* @see #add(int, Object)
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*/
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public boolean addAll(int index, Collection c)
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{
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Iterator ci = c.iterator();
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int size = c.size();
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ListIterator i = listIterator(index);
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for (int pos = size; pos > 0; pos--)
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i.add(ci.next());
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return size > 0;
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}
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/**
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* Get the element at a given index in this list. This implementation
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* returns listIterator(index).next().
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*
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* @param index the index of the element to be returned
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* @return the element at index index in this list
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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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// This is a legal listIterator position, but an illegal get.
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if (index == size())
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throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
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+ size());
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return listIterator(index).next();
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}
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/**
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* Obtain an Iterator over this list, whose sequence is the list order. This
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* implementation returns listIterator().
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*
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* @return an Iterator over the elements of this list, in order
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*/
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public Iterator iterator()
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{
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return listIterator();
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}
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/**
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* Remove the element at a given position in this list (optional operation).
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* Shifts all remaining elements to the left to fill the gap. This
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* implementation uses listIterator(index) and ListIterator.remove().
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*
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* @param index the position within the list of the object to remove
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* @return the object that was removed
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* @throws UnsupportedOperationException if this list does not support the
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* remove operation
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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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// This is a legal listIterator position, but an illegal remove.
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if (index == size())
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throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
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+ size());
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ListIterator i = listIterator(index);
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Object removed = i.next();
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i.remove();
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return removed;
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}
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/**
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* Replace an element of this list with another object (optional operation).
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* This implementation uses listIterator(index) and ListIterator.set(o).
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*
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* @param index the position within this list of the element to be replaced
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* @param o the object to replace it with
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* @return the object that was replaced
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* @throws UnsupportedOperationException if this list does not support the
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* set operation
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* @throws IndexOutOfBoundsException if index < 0 || index >= size()
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* @throws ClassCastException if o cannot be added to this list due to its
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* type
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* @throws IllegalArgumentException if o cannot be added to this list for
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* some other reason
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*/
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public Object set(int index, Object o)
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{
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// This is a legal listIterator position, but an illegal set.
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if (index == size())
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throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
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+ size());
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ListIterator i = listIterator(index);
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Object old = i.next();
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i.set(o);
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return old;
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}
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}
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