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From-SVN: r102074

libjava/classpath/java/util/AbstractSequentialList.java

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+/* AbstractSequentialList.java -- List implementation for sequential access
+   Copyright (C) 1998, 1999, 2000, 2001, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.util;
+
+/**
+ * Abstract superclass to make it easier to implement the List interface when
+ * backed by a sequential-access store, such as a linked list. For random
+ * access data, use AbstractList. This class implements the random access
+ * methods (<code>get</code>, <code>set</code>, <code>add</code>, and
+ * <code>remove</code>) atop the list iterator, opposite of AbstractList's
+ * approach of implementing the iterator atop random access.
+ * <p>
+ *
+ * To implement a list, you need an implementation for <code>size()</code>
+ * and <code>listIterator</code>.  With just <code>hasNext</code>,
+ * <code>next</code>, <code>hasPrevious</code>, <code>previous</code>,
+ * <code>nextIndex</code>, and <code>previousIndex</code>, you have an
+ * unmodifiable list. For a modifiable one, add <code>set</code>, and for
+ * a variable-size list, add <code>add</code> and <code>remove</code>.
+ * <p>
+ *
+ * The programmer should provide a no-argument constructor, and one that
+ * accepts another Collection, as recommended by the Collection interface.
+ * Unfortunately, there is no way to enforce this in Java.
+ *
+ * @author Original author unknown
+ * @author Bryce McKinlay
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @see Collection
+ * @see List
+ * @see AbstractList
+ * @see AbstractCollection
+ * @see ListIterator
+ * @see LinkedList
+ * @since 1.2
+ * @status updated to 1.4
+ */
+public abstract class AbstractSequentialList extends AbstractList
+{
+  /**
+   * The main constructor, for use by subclasses.
+   */
+  protected AbstractSequentialList()
+  {
+  }
+
+  /**
+   * Returns a ListIterator over the list, starting from position index.
+   * Subclasses must provide an implementation of this method.
+   *
+   * @param index the starting position of the list
+   * @return the list iterator
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
+   */
+  public abstract ListIterator listIterator(int index);
+
+  /**
+   * Insert an element into the list at a given position (optional operation).
+   * This shifts all existing elements from that position to the end one
+   * index to the right. This version of add has no return, since it is
+   * assumed to always succeed if there is no exception. This iteration
+   * uses listIterator(index).add(o).
+   *
+   * @param index the location to insert the item
+   * @param o the object to insert
+   * @throws UnsupportedOperationException if this list does not support the
+   *         add operation
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
+   * @throws ClassCastException if o cannot be added to this list due to its
+   *         type
+   * @throws IllegalArgumentException if o cannot be added to this list for
+   *         some other reason.
+   * @throws NullPointerException if o is null and the list does not permit
+   *         the addition of null values.
+   */
+  public void add(int index, Object o)
+  {
+    listIterator(index).add(o);
+  }
+
+  /**
+   * Insert the contents of a collection into the list at a given position
+   * (optional operation). Shift all elements at that position to the right
+   * by the number of elements inserted. This operation is undefined if
+   * this list is modified during the operation (for example, if you try
+   * to insert a list into itself).
+   * <p>
+   *
+   * This implementation grabs listIterator(index), then proceeds to use add
+   * for each element returned by c's iterator. Sun's online specs are wrong,
+   * claiming that this also calls next(): listIterator.add() correctly
+   * skips the added element.
+   *
+   * @param index the location to insert the collection
+   * @param c the collection to insert
+   * @return true if the list was modified by this action, that is, if c is
+   *         non-empty
+   * @throws UnsupportedOperationException if this list does not support the
+   *         addAll operation
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt; size()
+   * @throws ClassCastException if some element of c cannot be added to this
+   *         list due to its type
+   * @throws IllegalArgumentException if some element of c cannot be added
+   *         to this list for some other reason
+   * @throws NullPointerException if the specified collection is null
+   * @throws NullPointerException if an object, o, in c is null and the list
+   *         does not permit the addition of null values.
+   * @see #add(int, Object)
+   */
+  public boolean addAll(int index, Collection c)
+  {
+    Iterator ci = c.iterator();
+    int size = c.size();
+    ListIterator i = listIterator(index);
+    for (int pos = size; pos > 0; pos--)
+      i.add(ci.next());
+    return size > 0;
+  }
+
+  /**
+   * Get the element at a given index in this list. This implementation
+   * returns listIterator(index).next().
+   *
+   * @param index the index of the element to be returned
+   * @return the element at index index in this list
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
+   */
+  public Object get(int index)
+  {
+    // This is a legal listIterator position, but an illegal get.
+    if (index == size())
+      throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
+                                          + size());
+    return listIterator(index).next();
+  }
+
+  /**
+   * Obtain an Iterator over this list, whose sequence is the list order. This
+   * implementation returns listIterator().
+   *
+   * @return an Iterator over the elements of this list, in order
+   */
+  public Iterator iterator()
+  {
+    return listIterator();
+  }
+
+  /**
+   * Remove the element at a given position in this list (optional operation).
+   * Shifts all remaining elements to the left to fill the gap. This
+   * implementation uses listIterator(index) and ListIterator.remove().
+   *
+   * @param index the position within the list of the object to remove
+   * @return the object that was removed
+   * @throws UnsupportedOperationException if this list does not support the
+   *         remove operation
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
+   */
+  public Object remove(int index)
+  {
+    // This is a legal listIterator position, but an illegal remove.
+    if (index == size())
+      throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
+                                          + size());
+    ListIterator i = listIterator(index);
+    Object removed = i.next();
+    i.remove();
+    return removed;
+  }
+
+  /**
+   * Replace an element of this list with another object (optional operation).
+   * This implementation uses listIterator(index) and ListIterator.set(o).
+   *
+   * @param index the position within this list of the element to be replaced
+   * @param o the object to replace it with
+   * @return the object that was replaced
+   * @throws UnsupportedOperationException if this list does not support the
+   *         set operation
+   * @throws IndexOutOfBoundsException if index &lt; 0 || index &gt;= size()
+   * @throws ClassCastException if o cannot be added to this list due to its
+   *         type
+   * @throws IllegalArgumentException if o cannot be added to this list for
+   *         some other reason
+   * @throws NullPointerException if o is null and the list does not allow
+   *         a value to be set to null.
+   */
+  public Object set(int index, Object o)
+  {
+    // This is a legal listIterator position, but an illegal set.
+    if (index == size())
+      throw new IndexOutOfBoundsException("Index: " + index + ", Size:"
+                                          + size());
+    ListIterator i = listIterator(index);
+    Object old = i.next();
+    i.set(o);
+    return old;
+  }
+}