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dl |
1.1 |
/* |
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jsr166 |
1.10 |
* %W% %E% |
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dl |
1.1 |
* |
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jsr166 |
1.5 |
* Copyright 2006 Sun Microsystems, Inc. All rights reserved. |
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dl |
1.1 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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package java.util; |
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/** |
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* This class provides a skeletal implementation of the <tt>List</tt> |
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* interface to minimize the effort required to implement this interface |
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* backed by a "random access" data store (such as an array). For sequential |
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* access data (such as a linked list), <tt>AbstractSequentialList</tt> should |
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* be used in preference to this class.<p> |
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* |
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* To implement an unmodifiable list, the programmer needs only to extend this |
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* class and provide implementations for the <tt>get(int index)</tt> and |
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* <tt>size()</tt> methods.<p> |
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* |
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* To implement a modifiable list, the programmer must additionally override |
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* the <tt>set(int index, Object element)</tt> method (which otherwise throws |
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* an <tt>UnsupportedOperationException</tt>. If the list is variable-size |
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* the programmer must additionally override the <tt>add(int index, Object |
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* element)</tt> and <tt>remove(int index)</tt> methods.<p> |
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* |
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* The programmer should generally provide a void (no argument) and collection |
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* constructor, as per the recommendation in the <tt>Collection</tt> interface |
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* specification.<p> |
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* |
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* Unlike the other abstract collection implementations, the programmer does |
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* <i>not</i> have to provide an iterator implementation; the iterator and |
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* list iterator are implemented by this class, on top of the "random access" |
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* methods: <tt>get(int index)</tt>, <tt>set(int index, E element)</tt>, |
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* <tt>add(int index, E element)</tt> and <tt>remove(int index)</tt>.<p> |
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* |
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* The documentation for each non-abstract methods in this class describes its |
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* implementation in detail. Each of these methods may be overridden if the |
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* collection being implemented admits a more efficient implementation.<p> |
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* |
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* This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @author Josh Bloch |
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* @author Neal Gafter |
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jsr166 |
1.7 |
* @version %I%, %G% |
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dl |
1.1 |
* @see Collection |
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* @see List |
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* @see AbstractSequentialList |
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* @see AbstractCollection |
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* @since 1.2 |
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*/ |
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public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> { |
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/** |
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* Sole constructor. (For invocation by subclass constructors, typically |
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* implicit.) |
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*/ |
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protected AbstractList() { |
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} |
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/** |
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* Appends the specified element to the end of this list (optional |
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* operation). |
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* |
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* <p>Lists that support this operation may place limitations on what |
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* elements may be added to this list. In particular, some |
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* lists will refuse to add null elements, and others will impose |
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* restrictions on the type of elements that may be added. List |
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* classes should clearly specify in their documentation any restrictions |
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* on what elements may be added. |
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* |
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* <p>This implementation calls <tt>add(size(), e)</tt>. |
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* |
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* <p>Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> unless <tt>add(int, Object)</tt> |
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* is overridden. |
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* |
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* @param e element to be appended to this list |
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* @return <tt>true</tt> (as specified by {@link Collection#add}) |
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* @throws UnsupportedOperationException if the <tt>add</tt> operation |
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* is not supported by this list |
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* @throws ClassCastException if the class of the specified element |
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* prevents it from being added to this list |
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* @throws NullPointerException if the specified element is null and this |
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* list does not permit null elements |
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* @throws IllegalArgumentException if some property of this element |
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* prevents it from being added to this list |
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*/ |
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public boolean add(E e) { |
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add(size(), e); |
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return true; |
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} |
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/** |
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* {@inheritDoc} |
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* |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
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*/ |
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abstract public E get(int index); |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation always throws an |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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* @throws IllegalArgumentException {@inheritDoc} |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
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*/ |
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public E set(int index, E element) { |
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throw new UnsupportedOperationException(); |
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} |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation always throws an |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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* @throws IllegalArgumentException {@inheritDoc} |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
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*/ |
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public void add(int index, E element) { |
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throw new UnsupportedOperationException(); |
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} |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation always throws an |
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* <tt>UnsupportedOperationException</tt>. |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
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*/ |
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public E remove(int index) { |
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throw new UnsupportedOperationException(); |
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} |
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// Search Operations |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation first gets a list iterator (with |
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* <tt>listIterator()</tt>). Then, it iterates over the list until the |
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* specified element is found or the end of the list is reached. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public int indexOf(Object o) { |
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ListIterator<E> e = listIterator(); |
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if (o==null) { |
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while (e.hasNext()) |
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if (e.next()==null) |
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return e.previousIndex(); |
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} else { |
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while (e.hasNext()) |
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if (o.equals(e.next())) |
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return e.previousIndex(); |
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} |
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return -1; |
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} |
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/** |
176 |
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* {@inheritDoc} |
177 |
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* |
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* <p>This implementation first gets a list iterator that points to the end |
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* of the list (with <tt>listIterator(size())</tt>). Then, it iterates |
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* backwards over the list until the specified element is found, or the |
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* beginning of the list is reached. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public int lastIndexOf(Object o) { |
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ListIterator<E> e = listIterator(size()); |
188 |
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if (o==null) { |
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while (e.hasPrevious()) |
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if (e.previous()==null) |
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return e.nextIndex(); |
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} else { |
193 |
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while (e.hasPrevious()) |
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if (o.equals(e.previous())) |
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return e.nextIndex(); |
196 |
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} |
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return -1; |
198 |
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} |
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200 |
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201 |
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// Bulk Operations |
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203 |
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/** |
204 |
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* Removes all of the elements from this list (optional operation). |
205 |
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* The list will be empty after this call returns. |
206 |
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* |
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* <p>This implementation calls <tt>removeRange(0, size())</tt>. |
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* |
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* <p>Note that this implementation throws an |
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* <tt>UnsupportedOperationException</tt> unless <tt>remove(int |
211 |
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* index)</tt> or <tt>removeRange(int fromIndex, int toIndex)</tt> is |
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* overridden. |
213 |
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* |
214 |
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* @throws UnsupportedOperationException if the <tt>clear</tt> operation |
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* is not supported by this list |
216 |
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*/ |
217 |
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public void clear() { |
218 |
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removeRange(0, size()); |
219 |
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} |
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/** |
222 |
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* {@inheritDoc} |
223 |
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* |
224 |
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* <p>This implementation gets an iterator over the specified collection and |
225 |
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* iterates over it, inserting the elements obtained from the iterator |
226 |
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* into this list at the appropriate position, one at a time, using |
227 |
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* <tt>add(int, Object)</tt>. Many implementations will override this |
228 |
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* method for efficiency. |
229 |
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* |
230 |
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* <p>Note that this implementation throws an |
231 |
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* <tt>UnsupportedOperationException</tt> unless <tt>add(int, Object)</tt> |
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* is overridden. |
233 |
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* |
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* @throws UnsupportedOperationException {@inheritDoc} |
235 |
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* @throws ClassCastException {@inheritDoc} |
236 |
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* @throws NullPointerException {@inheritDoc} |
237 |
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* @throws IllegalArgumentException {@inheritDoc} |
238 |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
239 |
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*/ |
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public boolean addAll(int index, Collection<? extends E> c) { |
241 |
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boolean modified = false; |
242 |
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Iterator<? extends E> e = c.iterator(); |
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while (e.hasNext()) { |
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add(index++, e.next()); |
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modified = true; |
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} |
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return modified; |
248 |
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} |
249 |
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250 |
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// Iterators |
252 |
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253 |
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/** |
254 |
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* Returns an iterator over the elements in this list in proper |
255 |
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* sequence. <p> |
256 |
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* |
257 |
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* This implementation returns a straightforward implementation of the |
258 |
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* iterator interface, relying on the backing list's <tt>size()</tt>, |
259 |
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* <tt>get(int)</tt>, and <tt>remove(int)</tt> methods.<p> |
260 |
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* |
261 |
|
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* Note that the iterator returned by this method will throw an |
262 |
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* <tt>UnsupportedOperationException</tt> in response to its |
263 |
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* <tt>remove</tt> method unless the list's <tt>remove(int)</tt> method is |
264 |
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* overridden.<p> |
265 |
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* |
266 |
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* This implementation can be made to throw runtime exceptions in the face |
267 |
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* of concurrent modification, as described in the specification for the |
268 |
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* (protected) <tt>modCount</tt> field. |
269 |
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* |
270 |
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* @return an iterator over the elements in this list in proper sequence |
271 |
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* |
272 |
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* @see #modCount |
273 |
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*/ |
274 |
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public Iterator<E> iterator() { |
275 |
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return new Itr(); |
276 |
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} |
277 |
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278 |
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/** |
279 |
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* {@inheritDoc} |
280 |
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* |
281 |
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* <p>This implementation returns <tt>listIterator(0)</tt>. |
282 |
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* |
283 |
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* @see #listIterator(int) |
284 |
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*/ |
285 |
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public ListIterator<E> listIterator() { |
286 |
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return listIterator(0); |
287 |
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} |
288 |
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289 |
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/** |
290 |
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* {@inheritDoc} |
291 |
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* |
292 |
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* <p>This implementation returns a straightforward implementation of the |
293 |
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* <tt>ListIterator</tt> interface that extends the implementation of the |
294 |
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* <tt>Iterator</tt> interface returned by the <tt>iterator()</tt> method. |
295 |
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* The <tt>ListIterator</tt> implementation relies on the backing list's |
296 |
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* <tt>get(int)</tt>, <tt>set(int, Object)</tt>, <tt>add(int, Object)</tt> |
297 |
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* and <tt>remove(int)</tt> methods. |
298 |
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* |
299 |
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* <p>Note that the list iterator returned by this implementation will |
300 |
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* throw an <tt>UnsupportedOperationException</tt> in response to its |
301 |
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* <tt>remove</tt>, <tt>set</tt> and <tt>add</tt> methods unless the |
302 |
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* list's <tt>remove(int)</tt>, <tt>set(int, Object)</tt>, and |
303 |
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* <tt>add(int, Object)</tt> methods are overridden. |
304 |
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* |
305 |
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* <p>This implementation can be made to throw runtime exceptions in the |
306 |
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* face of concurrent modification, as described in the specification for |
307 |
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* the (protected) <tt>modCount</tt> field. |
308 |
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* |
309 |
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* @throws IndexOutOfBoundsException {@inheritDoc} |
310 |
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* |
311 |
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* @see #modCount |
312 |
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*/ |
313 |
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public ListIterator<E> listIterator(final int index) { |
314 |
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if (index<0 || index>size()) |
315 |
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throw new IndexOutOfBoundsException("Index: "+index); |
316 |
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317 |
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return new ListItr(index); |
318 |
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} |
319 |
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320 |
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private class Itr implements Iterator<E> { |
321 |
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/** |
322 |
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* Index of element to be returned by subsequent call to next. |
323 |
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*/ |
324 |
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int cursor = 0; |
325 |
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326 |
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/** |
327 |
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* Index of element returned by most recent call to next or |
328 |
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* previous. Reset to -1 if this element is deleted by a call |
329 |
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* to remove. |
330 |
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*/ |
331 |
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int lastRet = -1; |
332 |
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|
333 |
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/** |
334 |
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* The modCount value that the iterator believes that the backing |
335 |
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* List should have. If this expectation is violated, the iterator |
336 |
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* has detected concurrent modification. |
337 |
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*/ |
338 |
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int expectedModCount = modCount; |
339 |
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|
340 |
dl |
1.4 |
public boolean hasNext() { |
341 |
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return cursor != size(); |
342 |
dl |
1.1 |
} |
343 |
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|
344 |
dl |
1.4 |
public E next() { |
345 |
dl |
1.8 |
checkForComodification(); |
346 |
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try { |
347 |
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E next = get(cursor); |
348 |
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lastRet = cursor++; |
349 |
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return next; |
350 |
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} catch (IndexOutOfBoundsException e) { |
351 |
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checkForComodification(); |
352 |
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throw new NoSuchElementException(); |
353 |
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} |
354 |
dl |
1.1 |
} |
355 |
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|
356 |
dl |
1.4 |
public void remove() { |
357 |
dl |
1.1 |
if (lastRet == -1) |
358 |
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throw new IllegalStateException(); |
359 |
dl |
1.8 |
checkForComodification(); |
360 |
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|
361 |
dl |
1.1 |
try { |
362 |
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AbstractList.this.remove(lastRet); |
363 |
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if (lastRet < cursor) |
364 |
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cursor--; |
365 |
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lastRet = -1; |
366 |
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expectedModCount = modCount; |
367 |
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} catch (IndexOutOfBoundsException e) { |
368 |
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throw new ConcurrentModificationException(); |
369 |
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} |
370 |
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} |
371 |
dl |
1.8 |
|
372 |
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final void checkForComodification() { |
373 |
|
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if (modCount != expectedModCount) |
374 |
|
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throw new ConcurrentModificationException(); |
375 |
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} |
376 |
dl |
1.1 |
} |
377 |
jsr166 |
1.6 |
|
378 |
dl |
1.4 |
private class ListItr extends Itr implements ListIterator<E> { |
379 |
dl |
1.1 |
ListItr(int index) { |
380 |
|
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cursor = index; |
381 |
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} |
382 |
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383 |
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public boolean hasPrevious() { |
384 |
dl |
1.4 |
return cursor != 0; |
385 |
dl |
1.1 |
} |
386 |
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|
387 |
dl |
1.8 |
public E previous() { |
388 |
|
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checkForComodification(); |
389 |
|
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try { |
390 |
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int i = cursor - 1; |
391 |
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E previous = get(i); |
392 |
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lastRet = cursor = i; |
393 |
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return previous; |
394 |
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} catch (IndexOutOfBoundsException e) { |
395 |
|
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checkForComodification(); |
396 |
|
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throw new NoSuchElementException(); |
397 |
|
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} |
398 |
|
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} |
399 |
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|
400 |
dl |
1.1 |
public int nextIndex() { |
401 |
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return cursor; |
402 |
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} |
403 |
|
|
|
404 |
|
|
public int previousIndex() { |
405 |
dl |
1.8 |
return cursor-1; |
406 |
dl |
1.1 |
} |
407 |
|
|
|
408 |
|
|
public void set(E e) { |
409 |
|
|
if (lastRet == -1) |
410 |
|
|
throw new IllegalStateException(); |
411 |
dl |
1.8 |
checkForComodification(); |
412 |
|
|
|
413 |
dl |
1.1 |
try { |
414 |
|
|
AbstractList.this.set(lastRet, e); |
415 |
|
|
expectedModCount = modCount; |
416 |
|
|
} catch (IndexOutOfBoundsException ex) { |
417 |
|
|
throw new ConcurrentModificationException(); |
418 |
|
|
} |
419 |
|
|
} |
420 |
|
|
|
421 |
|
|
public void add(E e) { |
422 |
dl |
1.8 |
checkForComodification(); |
423 |
|
|
|
424 |
dl |
1.1 |
try { |
425 |
|
|
int i = cursor; |
426 |
|
|
AbstractList.this.add(i, e); |
427 |
|
|
cursor = i + 1; |
428 |
|
|
lastRet = -1; |
429 |
|
|
expectedModCount = modCount; |
430 |
|
|
} catch (IndexOutOfBoundsException ex) { |
431 |
|
|
throw new ConcurrentModificationException(); |
432 |
|
|
} |
433 |
|
|
} |
434 |
|
|
} |
435 |
|
|
|
436 |
|
|
/** |
437 |
|
|
* {@inheritDoc} |
438 |
|
|
* |
439 |
|
|
* <p>This implementation returns a list that subclasses |
440 |
|
|
* <tt>AbstractList</tt>. The subclass stores, in private fields, the |
441 |
|
|
* offset of the subList within the backing list, the size of the subList |
442 |
|
|
* (which can change over its lifetime), and the expected |
443 |
|
|
* <tt>modCount</tt> value of the backing list. There are two variants |
444 |
|
|
* of the subclass, one of which implements <tt>RandomAccess</tt>. |
445 |
|
|
* If this list implements <tt>RandomAccess</tt> the returned list will |
446 |
|
|
* be an instance of the subclass that implements <tt>RandomAccess</tt>. |
447 |
|
|
* |
448 |
|
|
* <p>The subclass's <tt>set(int, Object)</tt>, <tt>get(int)</tt>, |
449 |
|
|
* <tt>add(int, Object)</tt>, <tt>remove(int)</tt>, <tt>addAll(int, |
450 |
|
|
* Collection)</tt> and <tt>removeRange(int, int)</tt> methods all |
451 |
|
|
* delegate to the corresponding methods on the backing abstract list, |
452 |
|
|
* after bounds-checking the index and adjusting for the offset. The |
453 |
|
|
* <tt>addAll(Collection c)</tt> method merely returns <tt>addAll(size, |
454 |
|
|
* c)</tt>. |
455 |
|
|
* |
456 |
|
|
* <p>The <tt>listIterator(int)</tt> method returns a "wrapper object" |
457 |
|
|
* over a list iterator on the backing list, which is created with the |
458 |
|
|
* corresponding method on the backing list. The <tt>iterator</tt> method |
459 |
|
|
* merely returns <tt>listIterator()</tt>, and the <tt>size</tt> method |
460 |
|
|
* merely returns the subclass's <tt>size</tt> field. |
461 |
|
|
* |
462 |
|
|
* <p>All methods first check to see if the actual <tt>modCount</tt> of |
463 |
|
|
* the backing list is equal to its expected value, and throw a |
464 |
|
|
* <tt>ConcurrentModificationException</tt> if it is not. |
465 |
|
|
* |
466 |
|
|
* @throws IndexOutOfBoundsException endpoint index value out of range |
467 |
|
|
* <tt>(fromIndex < 0 || toIndex > size)</tt> |
468 |
|
|
* @throws IllegalArgumentException if the endpoint indices are out of order |
469 |
|
|
* <tt>(fromIndex > toIndex)</tt> |
470 |
|
|
*/ |
471 |
|
|
public List<E> subList(int fromIndex, int toIndex) { |
472 |
|
|
return (this instanceof RandomAccess ? |
473 |
dl |
1.8 |
new RandomAccessSubList(this, this, fromIndex, fromIndex, toIndex) : |
474 |
|
|
new SubList(this, this, fromIndex, fromIndex, toIndex)); |
475 |
dl |
1.1 |
} |
476 |
|
|
|
477 |
|
|
// Comparison and hashing |
478 |
|
|
|
479 |
|
|
/** |
480 |
|
|
* Compares the specified object with this list for equality. Returns |
481 |
|
|
* <tt>true</tt> if and only if the specified object is also a list, both |
482 |
|
|
* lists have the same size, and all corresponding pairs of elements in |
483 |
|
|
* the two lists are <i>equal</i>. (Two elements <tt>e1</tt> and |
484 |
|
|
* <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null : |
485 |
|
|
* e1.equals(e2))</tt>.) In other words, two lists are defined to be |
486 |
|
|
* equal if they contain the same elements in the same order.<p> |
487 |
|
|
* |
488 |
|
|
* This implementation first checks if the specified object is this |
489 |
|
|
* list. If so, it returns <tt>true</tt>; if not, it checks if the |
490 |
|
|
* specified object is a list. If not, it returns <tt>false</tt>; if so, |
491 |
|
|
* it iterates over both lists, comparing corresponding pairs of elements. |
492 |
|
|
* If any comparison returns <tt>false</tt>, this method returns |
493 |
|
|
* <tt>false</tt>. If either iterator runs out of elements before the |
494 |
|
|
* other it returns <tt>false</tt> (as the lists are of unequal length); |
495 |
|
|
* otherwise it returns <tt>true</tt> when the iterations complete. |
496 |
|
|
* |
497 |
|
|
* @param o the object to be compared for equality with this list |
498 |
|
|
* @return <tt>true</tt> if the specified object is equal to this list |
499 |
|
|
*/ |
500 |
|
|
public boolean equals(Object o) { |
501 |
|
|
if (o == this) |
502 |
|
|
return true; |
503 |
|
|
if (!(o instanceof List)) |
504 |
|
|
return false; |
505 |
|
|
|
506 |
|
|
ListIterator<E> e1 = listIterator(); |
507 |
|
|
ListIterator e2 = ((List) o).listIterator(); |
508 |
|
|
while(e1.hasNext() && e2.hasNext()) { |
509 |
|
|
E o1 = e1.next(); |
510 |
|
|
Object o2 = e2.next(); |
511 |
|
|
if (!(o1==null ? o2==null : o1.equals(o2))) |
512 |
|
|
return false; |
513 |
|
|
} |
514 |
|
|
return !(e1.hasNext() || e2.hasNext()); |
515 |
|
|
} |
516 |
|
|
|
517 |
|
|
/** |
518 |
|
|
* Returns the hash code value for this list. <p> |
519 |
|
|
* |
520 |
|
|
* This implementation uses exactly the code that is used to define the |
521 |
|
|
* list hash function in the documentation for the {@link List#hashCode} |
522 |
|
|
* method. |
523 |
|
|
* |
524 |
|
|
* @return the hash code value for this list |
525 |
|
|
*/ |
526 |
|
|
public int hashCode() { |
527 |
|
|
int hashCode = 1; |
528 |
|
|
Iterator<E> i = iterator(); |
529 |
|
|
while (i.hasNext()) { |
530 |
|
|
E obj = i.next(); |
531 |
|
|
hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode()); |
532 |
|
|
} |
533 |
|
|
return hashCode; |
534 |
|
|
} |
535 |
|
|
|
536 |
|
|
/** |
537 |
|
|
* Removes from this list all of the elements whose index is between |
538 |
|
|
* <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. |
539 |
|
|
* Shifts any succeeding elements to the left (reduces their index). |
540 |
|
|
* This call shortens the ArrayList by <tt>(toIndex - fromIndex)</tt> |
541 |
|
|
* elements. (If <tt>toIndex==fromIndex</tt>, this operation has no |
542 |
|
|
* effect.)<p> |
543 |
|
|
* |
544 |
|
|
* This method is called by the <tt>clear</tt> operation on this list |
545 |
|
|
* and its subLists. Overriding this method to take advantage of |
546 |
|
|
* the internals of the list implementation can <i>substantially</i> |
547 |
|
|
* improve the performance of the <tt>clear</tt> operation on this list |
548 |
|
|
* and its subLists.<p> |
549 |
|
|
* |
550 |
|
|
* This implementation gets a list iterator positioned before |
551 |
|
|
* <tt>fromIndex</tt>, and repeatedly calls <tt>ListIterator.next</tt> |
552 |
|
|
* followed by <tt>ListIterator.remove</tt> until the entire range has |
553 |
|
|
* been removed. <b>Note: if <tt>ListIterator.remove</tt> requires linear |
554 |
|
|
* time, this implementation requires quadratic time.</b> |
555 |
|
|
* |
556 |
|
|
* @param fromIndex index of first element to be removed |
557 |
|
|
* @param toIndex index after last element to be removed |
558 |
|
|
*/ |
559 |
|
|
protected void removeRange(int fromIndex, int toIndex) { |
560 |
|
|
ListIterator<E> it = listIterator(fromIndex); |
561 |
|
|
for (int i=0, n=toIndex-fromIndex; i<n; i++) { |
562 |
|
|
it.next(); |
563 |
|
|
it.remove(); |
564 |
|
|
} |
565 |
|
|
} |
566 |
|
|
|
567 |
|
|
/** |
568 |
|
|
* The number of times this list has been <i>structurally modified</i>. |
569 |
|
|
* Structural modifications are those that change the size of the |
570 |
|
|
* list, or otherwise perturb it in such a fashion that iterations in |
571 |
|
|
* progress may yield incorrect results.<p> |
572 |
|
|
* |
573 |
|
|
* This field is used by the iterator and list iterator implementation |
574 |
|
|
* returned by the <tt>iterator</tt> and <tt>listIterator</tt> methods. |
575 |
|
|
* If the value of this field changes unexpectedly, the iterator (or list |
576 |
|
|
* iterator) will throw a <tt>ConcurrentModificationException</tt> in |
577 |
|
|
* response to the <tt>next</tt>, <tt>remove</tt>, <tt>previous</tt>, |
578 |
|
|
* <tt>set</tt> or <tt>add</tt> operations. This provides |
579 |
|
|
* <i>fail-fast</i> behavior, rather than non-deterministic behavior in |
580 |
|
|
* the face of concurrent modification during iteration.<p> |
581 |
|
|
* |
582 |
|
|
* <b>Use of this field by subclasses is optional.</b> If a subclass |
583 |
|
|
* wishes to provide fail-fast iterators (and list iterators), then it |
584 |
|
|
* merely has to increment this field in its <tt>add(int, Object)</tt> and |
585 |
|
|
* <tt>remove(int)</tt> methods (and any other methods that it overrides |
586 |
|
|
* that result in structural modifications to the list). A single call to |
587 |
|
|
* <tt>add(int, Object)</tt> or <tt>remove(int)</tt> must add no more than |
588 |
|
|
* one to this field, or the iterators (and list iterators) will throw |
589 |
|
|
* bogus <tt>ConcurrentModificationExceptions</tt>. If an implementation |
590 |
|
|
* does not wish to provide fail-fast iterators, this field may be |
591 |
|
|
* ignored. |
592 |
|
|
*/ |
593 |
|
|
protected transient int modCount = 0; |
594 |
|
|
} |
595 |
|
|
|
596 |
dl |
1.8 |
/** |
597 |
|
|
* Generic sublists. Non-nested to enable construction by other |
598 |
|
|
* classes in this package. |
599 |
|
|
*/ |
600 |
dl |
1.1 |
class SubList<E> extends AbstractList<E> { |
601 |
dl |
1.8 |
/* |
602 |
|
|
* A SubList has both a "base", the ultimate backing list, as well |
603 |
|
|
* as a "parent", which is the list or sublist creating this |
604 |
|
|
* sublist. All methods that may cause structural modifications |
605 |
|
|
* must propagate through the parent link, with O(k) performance |
606 |
|
|
* where k is sublist depth. For example in the case of a |
607 |
|
|
* sub-sub-list, invoking remove(x) will result in a chain of |
608 |
|
|
* three remove calls. However, all other non-structurally |
609 |
|
|
* modifying methods can bypass this chain, and relay directly to |
610 |
|
|
* the base list. In particular, doing so signficantly speeds up |
611 |
|
|
* the performance of iterators for deeply-nested sublists. |
612 |
|
|
*/ |
613 |
|
|
final AbstractList<E> base; // Backing list |
614 |
|
|
final AbstractList<E> parent; // Parent list |
615 |
|
|
final int baseOffset; // index wrt base |
616 |
|
|
final int parentOffset; // index wrt parent |
617 |
|
|
int length; // Number of elements in this sublist |
618 |
|
|
|
619 |
|
|
SubList(AbstractList<E> base, |
620 |
jsr166 |
1.9 |
AbstractList<E> parent, |
621 |
|
|
int baseIndex, |
622 |
|
|
int fromIndex, |
623 |
dl |
1.8 |
int toIndex) { |
624 |
dl |
1.1 |
if (fromIndex < 0) |
625 |
|
|
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); |
626 |
dl |
1.8 |
if (toIndex > parent.size()) |
627 |
dl |
1.1 |
throw new IndexOutOfBoundsException("toIndex = " + toIndex); |
628 |
|
|
if (fromIndex > toIndex) |
629 |
|
|
throw new IllegalArgumentException("fromIndex(" + fromIndex + |
630 |
|
|
") > toIndex(" + toIndex + ")"); |
631 |
dl |
1.8 |
this.base = base; |
632 |
|
|
this.parent = parent; |
633 |
|
|
this.baseOffset = baseIndex; |
634 |
|
|
this.parentOffset = fromIndex; |
635 |
|
|
this.length = toIndex - fromIndex; |
636 |
|
|
this.modCount = base.modCount; |
637 |
|
|
} |
638 |
|
|
|
639 |
|
|
/** |
640 |
|
|
* Returns an IndexOutOfBoundsException with nicer message |
641 |
|
|
*/ |
642 |
|
|
private IndexOutOfBoundsException indexError(int index) { |
643 |
jsr166 |
1.9 |
return new IndexOutOfBoundsException("Index: " + index + |
644 |
dl |
1.8 |
", Size: " + length); |
645 |
dl |
1.1 |
} |
646 |
|
|
|
647 |
|
|
public E set(int index, E element) { |
648 |
dl |
1.8 |
if (index < 0 || index >= length) |
649 |
|
|
throw indexError(index); |
650 |
|
|
if (base.modCount != modCount) |
651 |
|
|
throw new ConcurrentModificationException(); |
652 |
|
|
return base.set(index + baseOffset, element); |
653 |
dl |
1.1 |
} |
654 |
|
|
|
655 |
|
|
public E get(int index) { |
656 |
dl |
1.8 |
if (index < 0 || index >= length) |
657 |
|
|
throw indexError(index); |
658 |
|
|
if (base.modCount != modCount) |
659 |
|
|
throw new ConcurrentModificationException(); |
660 |
|
|
return base.get(index + baseOffset); |
661 |
dl |
1.1 |
} |
662 |
|
|
|
663 |
|
|
public int size() { |
664 |
dl |
1.8 |
if (base.modCount != modCount) |
665 |
|
|
throw new ConcurrentModificationException(); |
666 |
|
|
return length; |
667 |
dl |
1.1 |
} |
668 |
|
|
|
669 |
|
|
public void add(int index, E element) { |
670 |
dl |
1.8 |
if (index < 0 || index>length) |
671 |
|
|
throw indexError(index); |
672 |
|
|
if (base.modCount != modCount) |
673 |
|
|
throw new ConcurrentModificationException(); |
674 |
|
|
parent.add(index + parentOffset, element); |
675 |
|
|
length++; |
676 |
|
|
modCount = base.modCount; |
677 |
dl |
1.1 |
} |
678 |
|
|
|
679 |
|
|
public E remove(int index) { |
680 |
dl |
1.8 |
if (index < 0 || index >= length) |
681 |
|
|
throw indexError(index); |
682 |
|
|
if (base.modCount != modCount) |
683 |
|
|
throw new ConcurrentModificationException(); |
684 |
|
|
E result = parent.remove(index + parentOffset); |
685 |
|
|
length--; |
686 |
|
|
modCount = base.modCount; |
687 |
dl |
1.1 |
return result; |
688 |
|
|
} |
689 |
|
|
|
690 |
|
|
protected void removeRange(int fromIndex, int toIndex) { |
691 |
dl |
1.8 |
if (base.modCount != modCount) |
692 |
|
|
throw new ConcurrentModificationException(); |
693 |
|
|
parent.removeRange(fromIndex + parentOffset, toIndex + parentOffset); |
694 |
|
|
length -= (toIndex-fromIndex); |
695 |
|
|
modCount = base.modCount; |
696 |
dl |
1.1 |
} |
697 |
|
|
|
698 |
|
|
public boolean addAll(Collection<? extends E> c) { |
699 |
dl |
1.8 |
return addAll(length, c); |
700 |
dl |
1.1 |
} |
701 |
|
|
|
702 |
|
|
public boolean addAll(int index, Collection<? extends E> c) { |
703 |
dl |
1.8 |
if (index < 0 || index > length) |
704 |
|
|
throw indexError(index); |
705 |
dl |
1.1 |
int cSize = c.size(); |
706 |
|
|
if (cSize==0) |
707 |
|
|
return false; |
708 |
|
|
|
709 |
dl |
1.8 |
if (base.modCount != modCount) |
710 |
|
|
throw new ConcurrentModificationException(); |
711 |
|
|
parent.addAll(parentOffset + index, c); |
712 |
|
|
length += cSize; |
713 |
|
|
modCount = base.modCount; |
714 |
dl |
1.1 |
return true; |
715 |
|
|
} |
716 |
|
|
|
717 |
dl |
1.8 |
public List<E> subList(int fromIndex, int toIndex) { |
718 |
jsr166 |
1.9 |
return new SubList(base, this, fromIndex + baseOffset, |
719 |
dl |
1.8 |
fromIndex, toIndex); |
720 |
|
|
} |
721 |
|
|
|
722 |
dl |
1.1 |
public Iterator<E> iterator() { |
723 |
dl |
1.8 |
return new SubListIterator(this, 0); |
724 |
|
|
} |
725 |
|
|
|
726 |
|
|
public ListIterator<E> listIterator() { |
727 |
|
|
return new SubListIterator(this, 0); |
728 |
dl |
1.1 |
} |
729 |
|
|
|
730 |
dl |
1.8 |
public ListIterator<E> listIterator(int index) { |
731 |
|
|
if (index < 0 || index>length) |
732 |
|
|
throw indexError(index); |
733 |
|
|
return new SubListIterator(this, index); |
734 |
|
|
} |
735 |
dl |
1.1 |
|
736 |
dl |
1.8 |
/** |
737 |
|
|
* Generic sublist iterator obeying fastfail semantics via |
738 |
|
|
* modCount. The hasNext and next methods locally check for |
739 |
|
|
* in-range indices before relaying to backing list to get |
740 |
|
|
* element. If this either encounters an unexpected modCount or |
741 |
|
|
* fails, the backing list must have been concurrently modified, |
742 |
|
|
* and is so reported. The add and remove methods performing |
743 |
|
|
* structural modifications instead relay them through the |
744 |
|
|
* sublist. |
745 |
|
|
*/ |
746 |
|
|
private static final class SubListIterator<E> implements ListIterator<E> { |
747 |
|
|
final SubList<E> outer; // Sublist creating this iteraor |
748 |
|
|
final AbstractList<E> base; // base list |
749 |
|
|
final int offset; // Cursor offset wrt base |
750 |
|
|
int cursor; // Current index |
751 |
|
|
int fence; // Upper bound on cursor |
752 |
|
|
int lastRet; // Index of returned element, or -1 |
753 |
jsr166 |
1.9 |
int expectedModCount; // Expected modCount of base |
754 |
dl |
1.8 |
|
755 |
|
|
SubListIterator(SubList<E> list, int index) { |
756 |
|
|
this.lastRet = -1; |
757 |
|
|
this.cursor = index; |
758 |
|
|
this.outer = list; |
759 |
|
|
this.offset = list.baseOffset; |
760 |
|
|
this.fence = list.length; |
761 |
|
|
this.base = list.base; |
762 |
|
|
this.expectedModCount = base.modCount; |
763 |
|
|
} |
764 |
dl |
1.1 |
|
765 |
dl |
1.8 |
public boolean hasNext() { |
766 |
|
|
return cursor < fence; |
767 |
|
|
} |
768 |
dl |
1.1 |
|
769 |
dl |
1.8 |
public boolean hasPrevious() { |
770 |
|
|
return cursor > 0; |
771 |
|
|
} |
772 |
dl |
1.1 |
|
773 |
dl |
1.8 |
public int nextIndex() { |
774 |
|
|
return cursor; |
775 |
|
|
} |
776 |
dl |
1.1 |
|
777 |
dl |
1.8 |
public int previousIndex() { |
778 |
|
|
return cursor - 1; |
779 |
|
|
} |
780 |
dl |
1.1 |
|
781 |
dl |
1.8 |
public E next() { |
782 |
|
|
int i = cursor; |
783 |
|
|
if (cursor >= fence) |
784 |
|
|
throw new NoSuchElementException(); |
785 |
|
|
if (expectedModCount == base.modCount) { |
786 |
|
|
try { |
787 |
|
|
Object next = base.get(i + offset); |
788 |
|
|
lastRet = i; |
789 |
|
|
cursor = i + 1; |
790 |
|
|
return (E)next; |
791 |
|
|
} catch (IndexOutOfBoundsException fallThrough) { |
792 |
|
|
} |
793 |
dl |
1.1 |
} |
794 |
dl |
1.8 |
throw new ConcurrentModificationException(); |
795 |
|
|
} |
796 |
dl |
1.1 |
|
797 |
dl |
1.8 |
public E previous() { |
798 |
|
|
int i = cursor - 1; |
799 |
|
|
if (i < 0) |
800 |
|
|
throw new NoSuchElementException(); |
801 |
|
|
if (expectedModCount == base.modCount) { |
802 |
|
|
try { |
803 |
|
|
Object prev = base.get(i + offset); |
804 |
|
|
lastRet = i; |
805 |
|
|
cursor = i; |
806 |
|
|
return (E)prev; |
807 |
|
|
} catch (IndexOutOfBoundsException fallThrough) { |
808 |
|
|
} |
809 |
dl |
1.1 |
} |
810 |
dl |
1.8 |
throw new ConcurrentModificationException(); |
811 |
|
|
} |
812 |
dl |
1.1 |
|
813 |
dl |
1.8 |
public void set(E e) { |
814 |
|
|
if (lastRet < 0) |
815 |
|
|
throw new IllegalStateException(); |
816 |
|
|
if (expectedModCount != base.modCount) |
817 |
|
|
throw new ConcurrentModificationException(); |
818 |
|
|
try { |
819 |
|
|
outer.set(lastRet, e); |
820 |
|
|
expectedModCount = base.modCount; |
821 |
|
|
} catch (IndexOutOfBoundsException ex) { |
822 |
|
|
throw new ConcurrentModificationException(); |
823 |
dl |
1.1 |
} |
824 |
dl |
1.8 |
} |
825 |
dl |
1.1 |
|
826 |
dl |
1.8 |
public void remove() { |
827 |
|
|
int i = lastRet; |
828 |
|
|
if (i < 0) |
829 |
|
|
throw new IllegalStateException(); |
830 |
|
|
if (expectedModCount != base.modCount) |
831 |
|
|
throw new ConcurrentModificationException(); |
832 |
|
|
try { |
833 |
|
|
outer.remove(i); |
834 |
|
|
if (i < cursor) |
835 |
|
|
cursor--; |
836 |
|
|
lastRet = -1; |
837 |
|
|
fence = outer.length; |
838 |
|
|
expectedModCount = base.modCount; |
839 |
|
|
} catch (IndexOutOfBoundsException ex) { |
840 |
|
|
throw new ConcurrentModificationException(); |
841 |
dl |
1.1 |
} |
842 |
dl |
1.8 |
} |
843 |
dl |
1.1 |
|
844 |
dl |
1.8 |
public void add(E e) { |
845 |
|
|
if (expectedModCount != base.modCount) |
846 |
|
|
throw new ConcurrentModificationException(); |
847 |
|
|
try { |
848 |
|
|
int i = cursor; |
849 |
|
|
outer.add(i, e); |
850 |
|
|
cursor = i + 1; |
851 |
|
|
lastRet = -1; |
852 |
|
|
fence = outer.length; |
853 |
|
|
expectedModCount = base.modCount; |
854 |
|
|
} catch (IndexOutOfBoundsException ex) { |
855 |
|
|
throw new ConcurrentModificationException(); |
856 |
dl |
1.1 |
} |
857 |
dl |
1.8 |
} |
858 |
dl |
1.1 |
} |
859 |
|
|
|
860 |
|
|
} |
861 |
|
|
|
862 |
|
|
class RandomAccessSubList<E> extends SubList<E> implements RandomAccess { |
863 |
dl |
1.8 |
RandomAccessSubList(AbstractList<E> base, |
864 |
jsr166 |
1.9 |
AbstractList<E> parent, int baseIndex, |
865 |
dl |
1.8 |
int fromIndex, int toIndex) { |
866 |
|
|
super(base, parent, baseIndex, fromIndex, toIndex); |
867 |
dl |
1.1 |
} |
868 |
|
|
|
869 |
|
|
public List<E> subList(int fromIndex, int toIndex) { |
870 |
dl |
1.8 |
return new RandomAccessSubList(base, this, fromIndex + baseOffset, |
871 |
|
|
fromIndex, toIndex); |
872 |
dl |
1.1 |
} |
873 |
|
|
} |
874 |
dl |
1.8 |
|